In various games, there are generally small chambers full to the brim of pots containing healing/revival items or even fairies located right next to boss rooms. Other than healing items, the pots might also hold something useful for defeating the boss—if you see Bombchus, you're gonna have to use 'em. Since boss rooms are marked on the map (and have huge, ominous doors), this isn't so much "suspicious" as "getting you ready for a fair fight"—however, mini-bosses aren't so marked, so if you find a fairy next to an otherwise nondescript door, get ready for a tussle.
Later 3D Zelda games gave you a fairy just before the Boss Room. In Twilight Princess, this is the only place where you can find fairies until you've completed a Side Quest. Fortunately, the Water Temple's boss room is relatively easy to access once you've beat the dungeon.
The Onimusha games have a tendency to throw herbs and medicine at you just before pitting you up against a boss.
In the 2D games, the map is very blatant about this — a dead end with a Save Room on one side, and... a giant glowing boss door on the other.
The older games did this, too: you'd usually find a pot roast along with a subweapon useful for the upcoming encounter. The most extreme example is before the final boss fight in Super Castlevania 4: if you jump off into space before ascending the steps to Dracula's room, you'll find an invisible platform that gives you two whip upgrades, 99 hearts, the cross (the best subweapon, bar none), and the two items that let you throw more than one item in a row. Considering how difficult Drac is, you'll need it.
Luigi's Mansion will often have a powerful healing item before the boss of each chapter.
In Cave Story, a secret room right above the entrance is available right before fighting the final bosses. They also had the healing machines and save points before some bosses.
Uncharted: Drake's Fortune is pretty generous with ammo placement and cover to hide behind throughout the game, but uses this trope a few times:
In Chapter 17 (the chapter where you first fight the zombie Spaniards), you're standing in a large, empty room that is stuffed to the gills with guns and ammo...because you're really gonna need it.
The same thing happens in Chapter 20 in the Nazi base.
A minor case in the sequel: at one point you're trapped in an ice chamber and find a WWII-era Nazi pistol on a long dead corpse during a mission where the game told the player they had no combat to worry about. Ostensibly, it's to shoot out some icicles blocking your way. However, as anyone who's played the first game would know, you're about to deal with something nasty.
Alundra and its sequel also make very heavy use of this trope. Save point, magic recharge and health recharge all in one place? Oh boy, you better get ready for some nightmare-spawned horror from out of this world. (Quite literally too, more often than not!)
After killing what you assume to be the boss of the final dungeon in StarTropics 2, you're thrown into a series of rooms filled with health powerups and medicine. Directly following is a marathon fight against every single boss in the game, directly followed by the final boss, who has two forms to boot. Ow.
Severance Blade Of Darkness does this in the final area of the game. One of the countless Dark Knights you'll be slaughtering will drop a key to the castle's armory. The armory contains the best weapons and armor for all four characters. However, all of these items can be found in earlier levels with the exception of the Barbarian who can ONLY find his ultimate weapon in the final stage.
The 2013 Tomb Raider reboot likes this. You'll be carefully exploring a new area, then: "Oooh, an ammo box! Ooh, another ammo box! ...and a quiver of arrows... in fact this whole room seems to be full of ammo boxes carefully stacked next to all those crates and low walls that are scattered around the floor and look suspiciously convenient for taking cover behind.... Oh Crap." "There she is! Get her!!" Cue siege event in which a couple of dozen enemies assault your position.
It's fairly easy to pinpoint the locations of the bosses in any Metroid Prime game by just looking on the map and finding save stations (which in some games also recharge your health) that are next to unusually large rooms. The 2D games (the ones with maps, anyway) get to the point and just label where bosses are on the map.
Metroid: Other M features one hell of an example in the room immediately preceding the Ridley battle. This room gives you an Energy Tank and an Accel Charge. It's the only room during the main run of the game where you can find multiple power ups, and it's a small room and both power ups are very easy to find. Not suspicious at all...
Not as "suspicious" (since it happens only after it's clear what you're up against), but the cutscene preceding the fight gives you access to both the Super Missiles and the Plasma Beam.
From this Let's Play thread for the hack Super Metroid Redesign: "Plus, if you take the bottom route, you find the most obvious missile expansion in the history of gaming, which gives you +10 missiles for some inexplicable reason. I feel like I'm being fattened up before the slaughter." Naturally, Kraid is a few rooms away. The same hack will mysteriously give you two Energy Tanks in an elevator room if you missed them earlier; this is because the next section ("Hell's Run", a trip through Norfair without the Varia Suit) is outright impossible without them.
In the Ninja Gaiden remake on the Xbox, if there is a crate of infinite arrows, there is at best a situation that requires you to use them, and at worst, a boss that can only be defeated by them. Interestingly, one of the reasons this game is Nintendo Hard is that they don't leave save points or items lying around right outside the boss room. True, the path to the fight is typically fairly easy, and you'll come to know it well, but count how many times you actually expect it when a boss fight to happen on your first playthrough.
In Crazy Flasher 2, you enter a small room with ammo all over the ground and several boxes containing health packs... and in the next room, you enter a pitched battle with a LOT of tough enemies.
Prototype has this in a mission where you have to hold off waves of infected mobs for a few minutes while Dr. Ragland does his work in a room protected only by reinforced glass and Alex lacks most of his powers. A rocket launcher, grenade launcher, machine gun, and assault rifle are conveniently laid in front of you once you resume control of Alex.
There are also a couple of missions in which you have to escort special plot-related military hardware in order to, well, advance the plot. Abandoned military vehicles, which are in tip-top operating status, are conveniently placed within reach so as to offer you a chance of less grief throughout the mission.
The final Rite in Quest For Glory V culminates in a battle right in the villain's storeroom, and wouldn't you know it, he succeeds in lifting the seal on the Dragonof Doom before you can stop him. Played with in that everything is locked behind a row of booby-trapped doors, requiring the player to work for it.
After needing to complete difficult puzzles in Another Code to get anywhere, one of the last rooms is full of goodies, and only two very simple puzzles. Enough to tense this player up for a Genre Shift.
Right before the last boss, you find a room with one of every kind of vending machine/powerup station in the game. It's almost like the city planners knew there would someday be an epic confrontation one room over.
At one point in the Medical Pavilion, you'll come across a room in which a you find your first shotgun. And, oh look, the game was generous enough to sprinkle some ammo around it. That was nice. So, of course, you pick up your new found weapon with enough ammo to last a frugal player a while. Then the lights go out...
It's also amusingly subverted when you confront Andrew Ryan—the rooms leading up to him are filled with ammo, health kits, and EVE, but he ends up ordering you to beat him to death without a fight.
And in the sequel, if there's a corpse for your Little Sister to harvest from, you can bet it will have at least one handy security or environmental measure in the area to help you fend off the Splicer hordes.
In Bioshock Infinite, look around for tears that change the scenery. If you can count more than three and at least one contains some sort of weapon, be prepared for a showdown.
Right before the final conflict in the engine room of the first game, Cortana reminds you that there's a huge, well-stocked armory station right down the hallway. What she doesn't mention is the active camouflaged Flood Warriors lurking inside.
Finding a rocket launcher or a fuel rod gun generally indicates an encounter with either enemy vehicles or Hunters up ahead.
Same for Halo: Reach in some levels. Right before you encounter your first Wraiths in the second mission, you are given a Target Locator. At the beginning of the level, there's a sniper rifle that you will definitely need on Legendary. The comms array building has a rocket launcher that can be used to take out the nearby Revenant. In Tip of the Spear, otherwise a Drought Level of Doom, you get a Revenant and a Plasma Launcher shortly before facing a pair of Hunters and a pair of Wraiths. On the Package, you are given a large stockpile of ammo and heavy weapons, including a BFG, for the lengthy Hold the Line episode at the end.
Another Bungie example is Marathon, which will do this often with health upgrades and ammo. A new gun, lots of refills, AND a triple boost to your health? SWEET! Thanks so much, man! ...why are the doors locked?note You hear a Pfhor's screech, followed by another, and another, and another...
If you see rockets, there will be a gunship (or worse, a strider). Lampshaded in Concerned. This may be linked to the fact that you physically can't destroy the gunship if there are no rockets around: They need at least three direct hits on easy, five on normal and seven(!) on hard, and you can only carry three.
Similarly, if you are ever given auto-turrets to set up, it means you are about to be swarmed by Combine or antlions.
After you defeat the hunter-chopper, you encounter a Combine base manned by a few metrocops, but packed to the brim with grenades, ammo, and health. Of course, after this the next combat situation you encounter is Ravenholm, where ammo is scarce and zombies are everywhere.
Your protective suit has 100 points of armour when fully charged, and the wall chargers can give you 75 points (on easy). When you make it into the Citadel at the end of the game, the wall chargers not only charge the HEV suit up to 200 points, they also refill your health, and they have a big charge reserve as well. Uh-oh.
2 plays it straight. In the last level, you start in a room filled with a Mega Sphere and every single weapon available in the game.
Also played straight in TNT: Evilution, where the final map does the same thing.
Doom's E2M8, too, giving you four Soul Spheres and a massive amount of every ammo type you're certain to have at that point. Not so much "generous", though, as, unless if you're really fast, you can only safely grab items from one of the four rooms they're placed in without alerting the Cyberdemon.
Cyberdemon battles are almost always preceded by you finding a massive supply of rockets and a rocket launcher, even though they take less damage from rockets than expectednote Cyberdemons and Spider Masterminds take no blast damage - the only damage a rocket deals is that of a direct hit.
Heretic's Shadow of the Serpent Riders ends with E5M8, Field of Judgement, where you're given all the weapons (other than the Firemace), a good load of ammo, one of pretty much every item in the game and a full load of big Phoenix Rod spheres at the center of the arena. Now why would they give you this generous loadout? You're going to need it all against the eight fucking Maulotaurs that the game throws at you for the final battle.
Every time you spotted ammo or health just laying somewhere, you could bet that somewhere behind you a door would slide open and something horrifying would shamble out and make you waste that newly-acquired health or ammo. Often, the monsters were scripted to show up if and only if you get the goods. The best strategy for saving ammo is not picking it up.
The last level of the game starts you off in a room with more gear than you could possibly carry! Unfortunately, it's mostly useless, because the only enemies these things will work on in the level are Maggots and Imps, handled easily enough with either the Shotgun or Chainsaw, and which you need to kill in order to charge up the Soul Cube, the only weapon that will work against the final boss.
One level (unsure if in the retail game or in Ro E, or in a mod...) played with this trope; you'd find a whole lot of goodies, and of course you'd tense up and expect the very gates to hell to open once you picked up all the stuff. Instead... nothing. So you gingerly keep going on, and after you turn a corner, then eleventy million monsters come forth and attack you. Doom was never as scary as in that point.
Whenever you see large amounts of ammo, healthpacks, armor and treasure in Will Rock, prepare for a fierce battle.
Medal of Honor has a rather laughable variant. If you see a mounted machine gun, you would expect a horde of enemies to come pouring out and attack when you use it. They do. But they're scripted to only come out when you use the gun... so if you walk past it, nothing.
Jedi Academy did this as well. There are blaster turrets set up twice on Hoth and once on Vjun. If you take control of them, the game spawns a horde of snowtroopers, an AT-ST, or 8 Hazard Troopers, depending on the turret. If you ignore them (especially likely on Vjun, given the only enemies in that area were trying to use that turret on you a second before), nothing happens.
Blood 2 also did this one time: the first invisibility pickup in the game is in a small room. If you go in and pick it up, a soul drudge spawns in the doorway (and promptly ignores you because of said invisibility). Leave the pickup alone and he won't spawn.
Most of the bosses in Wolfenstein 3D had a nearby room (usually secret, but not always) packed to the gills with health and ammo. And some of the individual levels. This caused most fun when the rooms were too packed, because the game's engine could only render so many objects at a time - and if there were too many in view, some would disappear. Including, potentially, the boss. (E4M10 and E6M9 are the best places to go to see this in action.)
In the original Far Cry, Jack gets access to an armory right after he defeats the supposed "final" boss, Krieger, and is heading to kill Doyle (the man who sold him out). Right after you visit this armory, you get locked into an arena with several armor-plated mutated creatures who all wield rocket and grenade launchers. Hope you stocked up.
Hold the Line sequences feature health, ammo, and sometimes a minigun. Justified in that the areas you hold off at are previously barricaded up by other survivors trying to hold out, or used as military extraction points, and thus were intentionally fortified and stocked with supplies at some point before you got there.
The miniguns are of limited use, though: they are fixed in place with limited field of view that often doesn't cover more than half the entry points, and are in highly exposed places. Usually takes the cooperation and cover of the entire team to give the minigun any tactical significance. It's often a more sound idea for the team to just back into a corner together.
The game does, however, manage to avert this trope for the most part. Since everything in the game (hordes, tanks, other specials, weapons, health items, explosives, even the "inbetween hordes" regular infected) is somewhat randomized and somewhat based on how well the player is doing (i.e., if you're doing good, you get less items, and have a greater chance of encountering Tanks and other Special Infected), large caches of weapons or items can just as often be indicative of a boss as they can an empty room. Even the "preset" Hold the Line hordes have extreme variability from one play to the next, making gauging the pacing of the game based on item handout all but impossible.
Left 4 Dead 2 plays this trope a bit more straight for the finale in "The Parish." Instead of the usual 4 med kits and 3 tier 2 weapons, you get 8 med kits and every possible tier 2 weapon, along with (randomized) pain pills, adrenaline shots, pipe bombs, molotovs, and sometimes even more first aid—in addition to several spots along the way with pills, new guns, and so on. The survivors need this because the finale involves dashing across a half-destroyed bridge jammed by abandoned cars. And infinite zombies.
One of the reasons the "Cold Stream" finale is hard is because it doesn't provide generous amounts of gear before its finale, which is an even harder uphill dash. Hopefully this will be amended before the map leaves beta-testing.
And let's not even talk about user-made campaigns. The first time most players walk into the supply room in the finale of "Questionable Ethics," you can the thunk over VoIP of their jaws hitting their desks: they've just seen a room that has four of everything, from pills to chainsaws. Then you hear the gears start spinning in their heads: "I've just survived Malevolent Architecture and Everything Trying To Kill Me, with infected literally falling from the ceiling. So far they've been doling out items—we're lucky to get a third of the health items we need, and we've found maybe five Tier 2 weapons total. But if they're giving us this room, what the hell's in the finale...?" Then you hear them scream.
Team Fortress 2: In the Mann Vs. Machine mission "Caliginous Caper", you and your teammates start out with 5000 credits to spend on upgrades (as opposed to the 400-1200 you normally start off with). You're gonna need them, because what follows is the hardest MVM mission in the game, which is also a Zombie Apocalypse.
Quake IV plays this trope dead straight. In the final level there is a long walkway going from the elevator where you start to the chamber with the boss and it is laden with health, armour and ammo for every gun you have.
Towards the end of the Nexus Hub level, there is a large room with a ridiculously large amount of ammo and health pick-ups in one corner. Enough to fully replenish your health and weapons, in fact. Shortly after, you discover some more pickups, including armour. In the very next room, you have to fight not just one, but two Stream Protectors (aka giant cybernetic spider-like monsters of doom) who not only pack flamethrowers, but homing rocket launchers as well. It gets worse when, upon their defeat, the Makron suddenly bursts through the door and kicks your ass.
One of the later stages also feature a big room with health, armour, and ammo scattered all over it. Right when you lick your lips and charge forth to loot the place, the doors lock and hard-to-kill monsters (Stream Protectors are only the first wave in this room) start spawning in waves. Lots of them.
Vivisector: Beast Inside - Found a large cache of health and ammo out in the middle of a clearing where you can't possibly not see the enemy coming a mile away? Expect to not only be ambushed by a bunch of Mooks teleporting in from nowhere, but also to be sealed up in the clearing by a convenient cage the moment you step near the bounty.
Turok 2 pushes this trope to its logical extreme: the penultimate boss is heralded by a long, narrow hallway containing a laundry-list of every weapon in the game and full ammo for each (in ascending order of power), plus the rare "more-than-maximum health" health pickup. The kicker? You literally cannot avoid these items.
Borderlands is usually pretty good about not doing this, but in one case it was made so obvious as to border on a lampshade. Directly before a large, perfectly circular room according to your map (in an area that has up until then been entirely cave), they give you two red chests (filled with ammo, grenades, and new weapons), and put an ammo vendor right there as well. Guess what's in the next room.
Alpha Prime has a room stocked full of ammunition and supplies in a mine right before the Final Boss. It's especially jarring here not only because the game had never done it before, but because you had been to an armory, and it wasn't anywhere near as well stocked (granted, much of the stuff in the armory was behind locked cabinets, though it still didn't have as much variety).
In Star Trek Voyager: Elite Force, right before you face the final boss there is a terminal that not only maxes out both kinds of ammunition, but raises them to 999 each, as opposed to the usual maximum of 200.
In the final level of the 1998 First-Person ShooterSi N, the player (who was tricked into a trap in the previous level) begins in a meat cart riding out into what looks like an empty cavern. You are then dropped into a pool of water, which leads to a massive cache of ammo, all the weapons in the game and a generous supply of health packs. Great, you say!...then you walk outside and see that the several-foot tall mutated father of the main antagonist is walking towards you with a tri-projectile rocket launcher. And the door to the supply room just closed behind you.
Medal of Honor: Frontline grants you a Gewehr, BAR and Bazooka, along with generous ammo, at the beginning of Clipping Their Wings. You're going to need it for the rest of the level.
Hack And Slash
In No More Heroes, a health pack, toilet, and sword-energy refill are awaiting Travis before every Boss Battle. Since the boss fights are pre-arranged duels, this is arguably justified.
Not to mention, his informant, Sylvia, will always call him on his phone (with her voice even heard on the mic if you're playing the Wii version), telling him to get ready (like going to the bathroom, which is game's save point) for upcoming boss.
A variant shows up in World of Warcraft occasionally. When an ally shows up to help you in boss battles, it's usually because you're really going to need them. For example, a chunk of the Blue Dragonflight shows up to help you against Kil'jaeden. Their main use is blocking Kil'jaeden's Darkness of a Thousand Souls ability, and they can only do it three times before everyone dies.
In the Heroic re-release of Zul'Gurub, there are often cauldrons lying around that give their users buffs. One type makes you mostly immune to nature damage, and it's used to go through a field of poison gas and fight two enemies with deadly poison breath (although they can also remove your immunity). Another type enables you to freeze enemies and take off most of their health, and it's used in areas with enemies that are stronger than most trash. Both types and a third, which causes players to cause AOE damage to enemies near them, are used in the fight against Zanzil; if he uses gas, you have to take the cauldron that makes you immune to it, if he summons a berserker, you have to freeze it, and if he summons zombies, you have to use the AOE damage cauldron against them.
You do not normally see a lot of this in Runescape; however, there is one glorious exception inside the God Wars Dungeon. Namely, right before the toughest boss in the entire game (upon writing), there's a bank that allows you to restock on items. The boss beyond has a combat level of 1001. In perspective, the highest combat level you, as a player, can get is 138. It really does speak for itself.
In Dungeons & Dragons Online, one of the first quests (possibly a Justified Tutorial) has you investigating disturbances in Heyton's Rest, the family tomb of LarsHeyton. At the beginning, you need to deal with cultists of the Devourer, who are busy disinterring corpses from the tomb, and are easily dispatchable with any weapon. About a third of the way into the tomb, you encounter a chest with a longsword and mace. Why? Because they're very useful for fighting skeletons (who are vulnerable to blunt damage) and zombies (who are vulnerable to slashing damage). Zombies and Skeletons take reduced damage from most weapon types and you will be fighting them shortly.
Halo Zero loves this trope. Here's a rocket launcher. Here's a Hunter or Sword Elite to use all of those rockets on. Here's a shotgun. Here's a clusterfuck.
Certain Kirby games (Super Star, Amazing Mirror, Squeak Squad, Return to Dreamland) have a habit of placing three "ability trophies" in the room before a boss encounter — though only occasionally are health powerups included. One game features a room with nothing but a sword ability trophy — and sure enough, the very next room contains Meta Knight, ready to duel you.
In Super Mario Galaxy, there is almost always a Life Mushroom shortly before the boss arena, either lying around or from a nearby shop.
If a Life Mushroom appears near the start of a level ... Oh Crap.
The Kid Chameleon level "Frosty Doom" is extremely generous with extra lives, including a guaranteed one for beating the level, knowing that a certain That One Level immediately follows: Bloody Swamp.
The last three bosses are preceded by large piles of weapons and ammo (and in one case health - in the other two your health is refilled automatically). In Iosa's case it merely confirms your suspicions, in Asha's case it's not at all surprising seeing as there's a logbook from him telling you he's waiting to kill you right before you enter the goodie room, and in Tor's case, it completely spoils the surprise that he is actually going to fight you, given that all the instructions up to that point are along the lines of "hopefully he'll be reasonable, if not you're screwed".
Ironically, the easiest way to defeat Tor is with the Resonance Reflector, which doesn't use ammo.
The room before fighting Yukabacera contains enough red nano to refill you from near-dead to full health about five times over. He drops even more when you kill him.
There's also plenty of powerups right before the elevator that leads to a Komato ship.
Beware Power Up potions in the game Hocus Pocus, the Monster is just about to show up (out of thin air)
The level Tree Tops in Spyro the Dragon features a suspicious amount of extra lives...probably because after that area you have to engage in tons of huge leaps across death-inducing falls, all while charging through rooms full of enemies that can gang up on you and kill you easily. Hence the Scrappy Level status.
For the entire Ratchet & Clank series, before every Boss fight/difficult section, there'll be a weapons vendor, for you to replenish ammo (and in some games, regenerate health, for some reason). Sometimes, they'll even pop out of thin air.
The Bonus Dungeon in Klonoa, Balue's Tower, hands you nine extra lives right at the beginning. While not a "boss," per se, consider that fair warning for what you're getting yourself into. 9-packs of lives occur at regular intervals throughout the level as well, usually just before long sections of horrible jumping puzzles.
Jett Rocket is usually quite stingy with its health-restoring items... except right before bosses. Then, you'll usually get a full top-up right before you fight them.
If you are playing a Mega Man game and you see an extra life and/or an E-Tank without a bottomless pit or a horde of instant death spikes around, you can pretty much know for sure that you'll find an insane platforming segment right in the following screen. Or a boss that will kill you in less than 30 seconds. Or both.
The Mega Man 4 fangame, Rockman 4 Minus Infinity has somewhat fair, if hard levels. Around the final boss, you're given an amazing amount of 1-Ups, E-Tanks, health, and ammo (pictured above). Then you fight the Wily Capsule. Which has 28 health bars. And a second form. Trust us when we say that you will need it all.
At the end of the second Wily (Shadaloo?) stage of Street Fighter x Megaman, you are given a 1-up, some health, and weapon energy right before the boss door. You'll be needing it for Vega.
Bleach: Soul Carnival 2 has health packs and SP items before boss fights or hard areas. Later stages also refill your BP.
In Yoshi's Island, the midway rings are always very conveniently placed before difficult sections or boss fights to act as a checkpoint. Some examples where this is apparent include the rings placed just before the skiing sections in the ice levels, the ring placed just before the killer drop past instant kill spikes in the Brutal Bonus Level Endless World of Yoshis, and the ones placed in every single room of the borderline Platform Hell Yoshis Island Easter Eggs level in the DS games.
A shutter rains down rings just before the final boss of Sonic Erazor.
Real Time Strategy
In the Homeworld single-player campaign, several missions, especially missions 7 and 8, feature very large amounts of resources. Coincidentally, each of those missions also features large enemy fleets which will likely do large amounts of damage to your fleet, requiring you to replace or rebuild much of it. The sequels don't have this so much, due to having much larger amounts of resources in general.
Any mission in a Real Time Strategy game where you start with large amounts of resources. Even (especially) if there is no enemy in the immediate vicinity, you will need those resources.
Related, if the mission begins with only basic structures, or with you having to build your first base by hand, expect the enemies to go easy on you for a while, not rushing your base or using the time to get a head start on an unstoppably huge army. If it begins with a full base or, even worse, an army, expect to use it immediately.
A common way of doing early in-game cutscenes would be to give you a vast amount of units and structures, then promptly nuke (sometimes literally) everything. Frequently happens in no-base scenarios where your powerful base is destroyed and you have to use a ragtag "escapee" force to finish the mission. Other ones involve spawning just enough units to kill the "heavy defended border" then give you your starting credits and base construction needs.
An incredibly painful example of this occurs in one Soviet mission during Red Alert 3. You're given 100,000 credits for you and your ally to build an army - enough to build five in fact - but just as the full extent of the enemy becomes clear, those credits are "shared" with a third general who shows up who you then have to fight shortly afterwards. So you have one enemy to deal with, then two, then three, then four...with no credits whatsoever. Ouch.
Most of the later caves in Pikmin 2 have a sublevel just before the cave's boss (or at least a very difficult section) with no enemies, lots of nectar, and lots of Candypop Buds.
While not a true Boss Battle, in Pokémon Mystery Dungeon, the presence of many loose items in a room usually (but not always) signals a "monster house" (a horde of enemies that teleport into the room, which you must kill or be killed).
Role Playing Game
Most RPGs often only provide save points right before major boss fights, so if you see one, be prepared to use it.
The Paper Mario games do this a lot. If you ever see a Health Block and a Save Block right next to each other in a Paper Mario game, you can bet there's a boss in the next room — even if you're not actually supposed to fight him. Case in point: there's a Health Block and a Save Block in Tubba Blubba's bedroom. (He'll enter after you're behind (from his perspective, not yours) his bed.) However, it's still handy; what follows is a chase back down into the Gulch, which is still littered with Hyper Clefts and Hyper Goombas. (Thankfully, the literal ghost town before your destination also has a Health Block and a Save Block...)
In the sequel, the room before the final boss not only comes with the aforementioned Save Block and Health Block, but also 1 of each of the best healing items in the game. Both of which you probably might need.
Final Fantasy kinda has this, since you can use tents at save points, and there is usually a save point right before each boss. This practice started with Final Fantasy IV, however. Programming limitations kept save points from being used in the NES games, and to this day, Final Fantasy III is the only game whose remakes still don't let you save right before a boss. Screw up or find an unwinnable battle in the Dark World? Enjoy climbing the Syrcus Tower from the ground floor again!
The beginning of the first Temple of Doom in Final Fantasy XII. When you first enter the area, you have the option to save (in a menu prompt, not a normal Save Point) and are fully healed automatically before having to fight a flying Mini-Boss that can be difficult without the proper equipment.
Save points in Final Fantasy games X through XII also heal and regenerate MP. It gets to the point where you start dreading the image of a save point deep within a dungeon.
There is one part of Final Fantasy X (Bevelle) where there were at least two save points in a linear corridor were less than a minute apart. Guess what followed the second one...
Also of note in that area are the random encounters; they give a very generous amount of AP (roughly 8,000 AP per battle). Given that Yuna has been missing for some time, the game may just be giving you a hint as to what you should consider doing before continuing...
And then we have the Omega Dungeon, who lacks the generosity. A Save Sphere at the start, have fun fighting yourself through powerful fiends, including the horrible Great Malboro who always starts with a ambush and then goes to inflict a variety of Status effects on your party.
Generally, Final Fantasy X gives the player several save points with not-so-large space in between. Not only the case in Bevelle, though that one is by far the worst offender. On the Thunder Plains, in one version, there's even a Save Sphere right outside the Travel Agency and one right inside it. And "right outside" and "right inside" means what it sounds like. You only need to walk 5 steps at most from you enter, until you reach the sphere. The outdoor one is right adjacent to the door, so it almost even blocks it.
When you arrive in Sanubia Desert, your party is split up. As you collect each member again, you may notice that the game is giving out a lot of healing items (of note are Al Bhed Potions, which heal statuses and restore 1000 HP to everyone; you'll reach the maximum 99 very fast if you do any sort of exploring). You may also notice that your only dedicated healer, Yuna, is the last person you need to find, where lots of healing items are abound. Guess who you won't be seeing for a long time...
One interesting example in Final Fantasy VII involves a point immediately after leaving Nibelheim. Traveling through an eerie passage, you get a savepoint at the very beginning of a largish room with a snakelike pathway, very innoculous, as many winding paths are common in areas throughout the game. In fact, there's a T-shaped intersection immediately after the save point. Head right, a chest and dead end. Head left, what some players consider That One Boss, Materia Keeper.
Anothe interesting example (in fact, a subversion) in this opus is the infamous "Yuffie savepoint". Upon defeat Yuffie (a random encounter in a forest), you will be brought to a screen with her, and taking the right choices in the dialog tree when you speak with her will make her join you. Since it's very easy to get answers wrong in the dialog tree, a savepoint is generously offered on the screen before talking to her. The subversion? Taking the save point requires you to turn your back on her, which let her assault you, steal your money and flee. Damn ninja!
After Yuffie steals the party's materia, the player would expect all the random encounters to be a nightmare since everyone is now crippled with stat changes and no abilities other than items and attack. However, the random encounters drop powerful items like X-Potions (full healing), Phoenix Downs (revive), and powerful attack items as compensation for a severely disadvantaged party.
In Final Fantasy IX, right before the first Black Waltz, there's a split path. On the left is a Moogle, which can save and heal you, and on the right is the cutscene for the boss. The problem is this: you need Vivi to free the Moogle from the block of Ice it's trapped in, but if you went right and then went back, Zidane's alone and Vivi can't help him. It doesn't help that the boss has to be fought with just Zidane, so if you went right first, Good Luck!
Baten Kaitos always has a save point before every boss battle... of course, since those are the only places in the game with the red save flowers (as opposed to blue), the game isn't particularly trying to hide the fact.
Tales of Vesperia has two kinds of save points: red ones, which are just normal save points, and blue ones, which restore your entire party's HP and TP. Take a wild guess as to where most of the blue ones are.
Tales of the Abyss did it too (first?), with yellow save points, and green save points that made a different sound effect.
Tales of Legendia was actually sort of the first (of the games released outside of Japan anyway). While save points were always the same, sometimes there'd be little circles next to them that, when checked, fully healed your party. They aren't usually as generously-placed as those in Abyss and Vesperia.
In Star Ocean: The Last Hope, purple spheres are save points and green spheres fully restore your HP/MP. If you see a green sphere, you can bet a tough fight is waiting for you ahead.
Parasite Eveand its sequel does this towards the end of the game where Aya meets up with the military and they give her all the items, weapons, and ammo she can hold.
Shin Megami Tensei I completely averts this. You're lucky if you get so much as a warning of the boss' location, much less anything to heal with.
Shin Megami Tensei II is nicer in this regard. After you've defeated three of the Elders/Archangels, the fourth one shows up, heals your party, and warns that there's still one enemy left. Cue fight with (false) Yahweh. Also, in the endgame, Steven will help you teleport to shops, healing garages and fusion temples to suit your needs, although you'll be sent back to the endgame area each time.
An utterly sadistic version was seen in Shin Megami Tensei if..., in the World of Greed. You will enter a room filled with valuable treasure, sixteen chests total. The next room, the local boss demon's power is directly linked to your greed. Forfeit the treasure and you will find a diminutive fox that can be easily destroyed. Take all of the treasure and face a titanic, Eldritch Abomination-level Kitsune of pure fog...
Every floor on Tartarus has a teleporter on it, acting as an emergency exit to the first floor if you're getting battered too much, but forcing you to redo that chunk of the tower if you take it. There are two-way teleporters that let you return to that floor afterwards, but there's always a boss fight on the same floor. The Answer, however, not only subverts this by forcing you to fight the boss to get to the teleporter, but adds some extra asshole points by putting the teleporter directly behind said boss, in clear sight.
There's also a variation on this, where the player can randomly stumble onto a floor crawling with nothing but Golden Shadows. However, this also means that TheReaper will be arriving much faster than usual.
Persona 4's idea of generosity is a warning before a mini-boss and a save point/Door To Before just before a dungeon's main boss. Given this lets you come back again another day fully refreshed (or, if you've befriended the fox, to get your Mana Meter refilled in the dungeon at great expense), and you can skip right back to the end of the dungeon, this is (like Persona 3) pretty generous for an Atlus game.
Right next to the boss's door in any Shadow Hearts game, you'll find a very convenient save point.
A form of this shows up in Mega Man Battle Network 6, where the spot in which the pre-boss cutscene kicks in is noted by a big skull on the floor. Considering how previous games left this up to "best guess" or "chronic paranoid saving", it's pretty generous. For that matter, so is the fact that most of the chips in the game can be acquired with "*" codes, preventing the "alphabet soup" problem that plagues many players while they're working through the main story mode.
Lufia loves this trope. Just a Save Point? Might just be a mid-point for the dungeon. Just a Health recharge? Okay, good fortune. Health and Magic recharge? Uh-oh. Health, Magic, and a Save Point? Alright, time to go fill my IP bar so this god-damned boss gets whacked a couple of times before he hurts me.
In ''Pokémon, guess what's in the Pokemon League Building? A combination Pokecenter and Pokemart.
Defused a bit in Pokémon Black and White, where there's a Mart inside every Center (not just the one in the league building).
At one point in Eternal Sonata, you rescue a boy, more from his mother finding out that he was missing than from the dangers of the cliffs, and are rewarded with a free stay at the inn. If you're thinking this is leading up to Inn Security, you'd be wrong; the night goes smoothly. Once you're done resting, however, go hit the Save Block near the entrance to Forte City; there's a boss battle ahead.
Just in case you managed to make it all the way through Fable without using a bow, there happens to be one sitting right outside the door on your way to the final showdown. Why? Because you can't hit him without it!
A variation on this occurs in Dungeon Siege, which has an auto-save feature. Whenever it says 'auto-saving', a big fight or a hard dungeon is coming up.
If the Kingdom Hearts series does this, it's at least more subtle than other games, as all save points regenerate health and magic, no matter where they are. The more obvious clue is your characters all walking around independently and talking to you.
The practice is spoofed in the Chain of Memories manga where, right before the fight with Marluxia, Sora and Co. come across a vending machine full of health and mana potions. And they get several for free.
Dragon Age: Origins often averts this, being quite unforgiving at certain points of the game, if the player didn't think to stock up enough healing poultices, but plays it straight in a couple of points, as well, like just before the final battle with the Archdemon, where you encounter a storage room full of useful items - in locked chests. Hopefully you remembered to take your rogue along.
Injury Kits are generally a good indicator of an ambush ahead. Except when they come one fight too late.
Played straight in the quest A Paragon of Her Kind, where a large supply of potions is stored just around the corner from the boss fight.
Dragon Age II, on the other hand, auto saves before huge battles. When walking along a path and you see the save icon appear, you become suspicious that a dragon is about to attack you...
Single corpses and skeletons also tend to drop multiple potions and droughts before big boss battles, like the Ancient Rock Wraith.
As you can save pretty much anywhere in Sands of Destruction, the game is fairly generous in providing healing points before boss battles.
In Dragon Quest VIII, there's a spring deep inside one dungeon that fully restores all your hit points and magic points when you step into it. Sure enough, just past the spring is Dhoulmagus, one of the hardest boss fights in the game.
MOTHER 3 lampshades this, to an extent, towards the end of New Pork City. As you're told every time you clear a floor that the next room up is supposedly the 100th floor with the final boss chamber, there's always a save frog before the door to keep the player on their toes.
When Mass Effect 2 gives you the opportunity to switch weapons in the middle of a level, odds are there's a big fight waiting for you a few rooms away.
Somewhat inverted in Mass Effect games. Generally, the medi-gels and the spare ammo (in 2) are actually in the room where the gigantic climactic battle of the level is. However, you rarely actually run out of medi-gel in the middle of a battle, so it's more for replenishing your depleted stores after the battle is done. Ammo, on the other hand, is a different matter.
In full effect in Mass Effect 2 on the Collector ship, where you get access to advanced weapons training about 5-10 minutes before one of the hardest battles in the game. There's also a lot of unusually high-value salvage and some research to unlock before the fighting starts, which only adds to the sense that something big is about to happen, but you can't use any of your new goodies besides the weapons training until the mission is over.
All those flamethrowers you find laying around in the rachni hive in Mass Effect 3 are bound to make you nervous. Naturally, they come in very handy against the webs, pods/sacs, and various creepy enemies.
At several points in Mass Effect 3 you'll find a Heavy Weapon that you can pick up, either the Hydra Missile Launcher, Blackstar, or Geth Spitfire. These will always be placed in conjunction with a particularly tough battle, though in a bit of a subversion they're frequently in the battle area and aren't always placed somewhere that's convenient or safe to get to, making it a bit risky to go for them.
In Deus Ex: Human Revolution ammo is extremely scarce, so this trope is played straight for every boss battle, Especially for the fight against Yelena Fedorova, before which you are given a bloody minigun and about 150 ammo for it.
Inside Isaiah Sandoval's apartment you find a conspicuous Praxis Point on top of a corpse. Sounds legit, right?Taking it triggers an EMP mine and causes any nearby mooks to gun for you.
The first phase of the final dungeon is full of rare weapons and ammo, but has no enemies at all. You just know something bad's on its way.
Zig zags in Knights of the Old Republic II where the game tells you very early on that Atton has a special ability to guess when things about to get bad. The idea is that whenever he quotes the iconic line; "I have a bad feeling about this", you are advised to save the game. The problem? Like every other non-combat-oriented special ability the player's companions get, this only happens once in the entire game.
Fallout 3: In the Calvert Mansion from the Point Lookout DLC, there is an abundance of stimpacks and ammo throughout. You'll use nearly all of it when fending off the Tribal attacks.
Done in all the Mario & Luigi games. If there's a handy save point nearby (along with a few blocks containing useful healing items), you almost certainly know there's a difficult section or Boss Battle nearby. It's most notable in Mario & Luigi: Dream Team though, since you don't have the Save Game Limits of only being able to save at save points any more, hence any you do see are placed just right to act as a 'save here reminder' for anyone new to the game. Along with the inevitable healing items in blocks, shops, etc.
Raystorm also does this in Extra Mode of Home Editions of the game. Just before the Stage 7 boss. Then Stage 8 is a boss fight itself.
Stealth Based Game
In Metal Gear Solid, you are suddenly advised to save your progress by an ally that never suggested so before. What happens afterwards? You enter an scene where dying is permanent. (A.K.A. you can't press continue)
Silent Hill 2 has no fewer than nine savepoints in the room immediately before the final boss battle, arranged in a square on the wall. This is more of a really heavy hint than generosity as such (since it's not actually any more effective than a single savepoint), but still. Silent Hill Origins does something similar in a Shout-Out.
In Silent Hill: Homecoming, unless you use your guns incredibly sparingly, you will be low on ammo for most of the game. In the sewer level, you get given several boxes of ammo for both the pistol and shotgun. Guess what? Eventually you come to a small room where you have to fight three needlers, who block most of your attacks, and a siam, who takes three shotgun blasts form close range to the head to kill. Have fun.
Silent Hill 3 spawns additional ammo and health items when you're low on supplies. Specifically, it provides more medical supplies when you are low on ammo and more ammo when you are low on medicine. It even lampshades it in a cutscene.
Alan Wake does this at least a few times. Your usual pickups come from the occasional red emergency box lying around, which will have batteries for your flashlight and a little bit of ammo. So when you find multiple boxes of ammo, flares, batteries, etc. lying around an area, you know that you're about to walk into a massive assault by The Taken. It also manages to invert the trope: any section where Alan has lost his light and/or weapons will usually have few or no enemies, simply because he'll have no way to fight them.
At one point Alan himself comments on how suspicious it is finding flashbang grenades amongst supplies left by the power company. Of course, Alan himself probably wrote them there.
In every The House of the Dead game, you can unlock a special bonus room full of bonus-point items and life-ups just before the Final Boss by fulfilling a hard-to-meet requirement—in the first 3 titles, this requirement is rescuing every hostage or rescuing your partner at every chance. In The House of the Dead 4, you have to one-credit the game up to that point. If you're looking to clear the entire game without any continues or going for a high score, this will really help.
Resident Evil 4 lets on that a major encounter is ahead when you find The Merchant (and his armory) and a typewriter in the most implausible of locations.
Also done through the chapters containing the Regeneradors via means of ammo - rifle ammo not only becomes increasingly scarce, but finding any rifle ammo (which is always 3-4 bullets) becomes a sign there's a nigh-invulnerable monster that requires ~4 bullets to kill ahead.
In Dead Space, there are two points where you find save points: in the "safe room" where you can restock equipment and items, and right before something big is going to happen. Finding a Store or Save Point on its own isn't that bad, but finding both in the same place? You're about to have your ass firmly handed to you.
It gets even more ridiculous when you see an oxygen recharge station placed randomly in an area. When you see one you know eventually the air will be let out of an area.
On the other hand, since certain levels are reused, that means the air may be let out five minutes from now, or five chapters from now.
In Ghosthunter there's a major ammunition cache in the final level. It's useless because shortly after that Lazarus loses all his weapons. The final battle uses a new weapon with infinite ammo.
Eternal Darkness subverts and plays it straight. Played straight in that the one time the game asks if you want to save, it's just before teleporting you to the final boss. Subverted in that several actions (such as diverting gas or opening a door) give you the choice of whether to go through with it or not, regardless of the fact that you need to do it to proceed and that nothing happens on most occasions. A major exception to this is at the end of Paul Luther's chapter, where you get a warning of sorts when you reach the Black Guardian's lair, and instantly die upon crossing it.
This is also one of the game's Sanity effects: you find mountains of ammo in a room, but before you can even collect all of it you appear in the previous room... without all the ammo you just picked up.
Cryostasis is forced into this by the game mechanics—rather than having health in the proper sense, you have body heat, which is slowly depleted by your environment and rapidly depleted by monsters. If you get to warm your hands by a fire, it means you're about to get very, very cold.
Jet Force Gemini normally has no-enemy rooms with enough Five Unit Gemini's to fully heal you just about all of the time; it also has plenty of ammunition; this is a very good thing, since most of the bosses are incredibly difficult.
Terminator: Salvation lets your character see the green outline of any weapons in the area, even through walls, so when you see a big pile of green, or just green in the shape of a rocket launcher, you know a whole bunch of big machines are gonna be coming at you.
In Freedom Fighters, Rocket Launchers will only appear when you have a helicopter or a heavily fortified encampment to deal with up ahead, and Sniper Rifles are usually placed in locations where you can expect to use every single bullet before running out of enemies.
In Mega Man Legends Data who refilled your special weapon, restored your health, and saved your game had a weird habit of popping up JUST before a boss fight..
In Kid Icarus: Uprising, if you stumble across a Drink of the Gods (fully restores your health), chances are you're going to meet the boss of the level just after. It isn't always the case, tough, but they still tend to pop-up where you're going to need a fully refilled health bar.
Turn Based Strategy
Cruelly subverted in Final Fantasy Tactics. There are certain parts of the game where battles occur one after the other, and the game kindly lets you save in the intermission between each part. Unfortunately, what the game doesn't tell you is that once you've passed the first part of these multi-battle sequences you cannot leave to level up or buy items. There's one area in particular that drops two nasty boss fights on you right after a relatively easy battle. You might need to fall back to your secondary save file to raise your team up a few levels. Unless you didn't make one...
In Fire Emblem: Blazing Sword, there is a chapter where literally all there is is shopping for weapons, staves, and healing items. It comes right before the penultimate chapter, which has a huge number of enemies, including a dangerous boss, and then the final chapter where you have to fight about ten reincarnations of previous bosses, and then the "final" boss, and then the real final boss all without saving in the middle, so if you die, you have to fight every single one of them over again.
The final chapter of Path of Radiance features two: the shop sells Physic staves for the first time (unless you're on the Japan-onlyManiac Mode), which are incredibly useful for the followinmg boss fight. Secondly, the Hard Mode version of the chapter actually has less enemies than Easy/Normal. There's a very good reason for this... the final boss actually moves now, and gets a new One-Winged Angel form when he goes down the first time.
Open-book/open-note exams. In principle, they sound like a breather since you don't have to memorize the material. In reality, it's often a carte blanche for the professors to make you wish you had memorized the material.
These are more for "did you understand the material?" checks. The real world forgives you if you have to open a book, notebook, etc. What the real world doesn't forgive is if you don't understand the material well enough to create a quality product even with those aids (and especially if that product involves human lives)
In advanced Engineering classes, these are sometimes "Open Note", "Open Book", and "Open Prior Exams that are posted on the internet with solutions". The rationale is that as an engineer, you will have access to your notes, your texts, and your past work. Note, these tests still have a high fail rate.
A common justification given by teachers is that the process of writing notes and cribsheets right before an exam is an excellent form of review; and in many cases, once the notes have been written, they are not necessary (assuming the students are taking the time to write their own notes).
Next time you have a math/calculus/physics/statistics exam, if you see the professor stand up, go to the whiteboard and write down formulas before starting, do not rejoice. You'll need them.