Clonk started out as a 2D fighting game much like Worms, but also contains elements of a strategy game, especially in the rounds with a "Settlement" or a "Mining" goal, adventure game in the rounds with a set story, a plain wide open sandbox game, and with all the expansion packs and downloadable content, you can well give it fantasy, western, cyberpunk, racing, heck, even zombie survival game elements as well.
Knights in the Nightmare defies easy description. It's a Real Time/Turn-Based Strategy Hybrid which incorporates Bullet Hell elements because the enemy is shooting at the game cursor, not the units temporarily brought to life to attack back. There are RPG Elements for the units being controlled, but there's some stuff that can't even properly be classified, like hitting a big red/blue switch for Law and Chaos that completely changes the hit ranges and attack types for your characters across the map, or that enemy placement is decided by a roulette system.
Batman: Arkham Asylum is often classified as an action adventure as the game is about equal parts combat and interacting with the environment. However, the game mixes in elements of stealth and survival horror, contains RPG Elements, has rhythm-based combat, and is also a Metroidvania game.
Persona 2 is an RPG Urban Fantasy about saving the world and facing your fears and with psychological elements and it's a horror game like the other Megatens and it's got elements of romance. Confusing stuff. Persona 3 and the Persona games that followed are all that but with dating sim mechanics. Hmm...
Monday Night Combat at first looks like another Third-Person Shooter, but teamwork is vital, playing deathmatch style tends to do as much harm as good, you're effectively fighting on a two-sided Tower Defense game, you've got to upgrade your abilities and buy bots with money you earn during battle, and topping it all off it's class-based to keep things balanced.
Fantasy Earth Zero: Most of the game is typical MMO stuff, but the main heart of the game is basically 100-man PvP RTS/Tower Defense.
Sacrifice is a fantasy third person RPG, RTS game.
Brütal Legend starts as a Hack-and-Slash game with a dash of racing, but later becomes a RTS-Hack and Slash game with some racing side missions and occasional rhythm-based segments.
An in-universe example, the crappy Fake Band Kabbage Boy that Eddie is stuck working for in the opening cutscene actually has their song unlockable for the in-game radio (Eddie even audibly groans when you unlock it). If you sort songs by genre, it's listed under "Second Wave of American Tween Melodic Rap Metalcore". It's the only song in that category, of course.
Achron is superficially an RTS, but the time travel mechanics make it play quite differently. The creators call it a "Meta Time Strategy Game".
Pathologic and Turgor, by Ice Pick Lodge. They're both first person action-adventure surreal/lovecraftian horror philosophy art games where the aim isn't really to kill things but you're probably going to be doing that in the process of whatever other endeavor you have.
Getter Love!! is a combination of a board game, a dating simulator, a few free-motion mini-games, and all kinds of hilarity, including hip-wiggling panda bears. Plan out where you want to go, use item cards to promote your relationships or screw your opponents over, talk to your friends or one of seven girls, take the girl of your choice out to places, buy presents for your girl of choice, and even run into various random folks. Watch out for the resident Gonkwho wants to harass youand fuck up your relationships! All kinds of wacky hijinx ensues until someone confesses their love, after which either either school resumes or the winner's girl appears in a pastel-colored aura while talking to you.
Hatoful Boyfriend: Oh, look, another Visual Novel / Dating Sim. Oops, it has just turned into a horror game. And just like that, now, it's a turn-based RPG. And, after you thought it can't get any weirder, it turns into a survival horror/mystery With pigeons.
Deadly Premonition is a survival horror adventure wide-open life sim—and that's just the gameplay. The story attached to it is a murder mystery police procedural horror-fantasy romance that ping-pongs between nightmarish tragedy and screwball comedy, with every mood in between.
Folk Tale is a city-builder and survival game, as you must build a village with various services, harvest resources, keep your denizens happy and well-fed, while your manpower is one of your resources. It also has a typical Strategy RPG gameplay, as each villager has stats, experience levels, inventory slots, and can be manually controlled while they aren't working; also, some of the available jobs are purely military, instead of classical services like farmer, miner, lumberjack, hunter, etc.
Borderlands. From a story standpoint, it's a Black ComedySpace Western. From a gameplay standpoint it's a First Person Shooter with classic RPG elements (although that latter category is rapidly becoming a game genre in itself).
Overwatch is an unlikely mixture of a team-based First-Person Shooter in a Pixar-like setting. The roster of colorful characters can be compared to that of a Fighting Game, while each character brings a unique influence into the game to give it something with far more personality than your standard FPS.
LittleBigPlanet: Try explaining this to someone who hasn't really played it. The first game is a platformer, but encourages you to build whatever kind of level you want, whether it be an actual level in the vein of Mario or just a music or set-piece showcase. The second game, however, looks to embrace this wholeheartedly, as it was marketed as a platform for games rather than a platform game. The main game showcases some unique gameplay styles, including a side-scrolling shooter that looks like a retro arcade game. The overall effect is a mashup of Gmod for consoles, Mario, winks and nods toward Monty Python-style humor, and sinister weaponized cuteness.
The Guild series is about managing a medieval family on several generations to become a successful business dynasty and an important local political actor. Its gameplay is a RPG (each dynasty members' has stats and perks), management game (running your businesses, creating gold, and managing your crew), and Sims-like (finding a spouse and have children, as well as managing relationships to have friends and allies) hybrid.
Battle Chef Brigade is a mix of action-platformer with puzzle game mechanics; players hunt monsters for ingredients, then use a puzzle game interface to cook the ingredients in an Iron Chef-style competition.
The obscure Sega CD game Revengers of Vengeance featured a campaign mode that combined a fighting game with RPG mechanics and vertical shmup levels.
Prismata takes concepts from real time strategy and card games, even though it's a turn based game with no cards.
Super Daryl Deluxe is a metroidvania/RPG/sidescrolling brawler with an extremely surreal style.
All the original Might and Magic games switch from swords and sorcery to sci-fi towards the end. Trade in your maces and bows for blasters.
Rockstar's Red Dead Redemption. Wide Open Sandbox with focus on typical RPG elements like looting, morality and NPC interaction and the inclusion of a hunting system while still maintaining the third person shooter aspect and an even wider world designed for exploration and adventure..
Thief: Although it has since been recognized as a "first person stealth" game, journalists had trouble sorting it into any recognisable genre when it came out in November 1998. It plays from a first person perspective, yet it doesn't award killing like an FPS. It features lots of various puzzles, yet isn't an Adventure Game. It includes RPG Elements, yet isn't an RPG at all. Along with Metal Gear Solid, Thief practically defined the stealth game genre as we know it today.
Deadly Rooms of Death is part puzzle game, part hack and slash, part turn based strategy, and ultimately none of those things. The only classification it can consistently fit is that of extremely difficult games.
Planetarium bills itself as an online "story-puzzle", and is about equally balanced in both Web Original and Puzzle Game elements. You can follow the unfolding story and ignore the puzzles, or focus more on the puzzles than the story surrounding them, or enjoy both the story and puzzles.
NiGHTS was designed as roughly a platformer, but is far removed from the genre's core concepts: As you're in midair nearly all of the time, there's no actual running, jumping, or functional platforms. The stages loop endlessly, as your goal is collection rather than getting to the end. You're totally invincible, your only real opponent being the timer counting down. You must reach certain score quotas to advance. And sometimes, you transform into a bobsled. Indeed, you have just as many who say it's a platformer as those who say it isn't, and the only other genre it fits even microscopically into is as a Horizontal Scrolling Shooter with no shooting and total free roaming.
Gobtron. You play as a giant pink monster and defend against waves of enemies by using its snot, spit, burps and farts.
Don't Shoot the Puppy doesn't fit into any genres of video games; in fact, it's barely a video game at all as you will trigger a sentry gun shooting a puppy if you so much as move the mouse, regardless of distractions like messages that it's okay to move the mouse and the puppy seemingly stopping. As an extra middle finger to the player, not moving the mouse after one level can cause the game to time out.
Blast Corps starts out hard to classify, what with the main goal being to rush in front of a runaway missile carrier with a motley assortment of increasingly-bizarre demolition vehicles to level anything in its path before it crashes. Then it starts turning into a puzzle as levels feature things like arranging cargo ships so the carrier can roll over water. Then it gains exploration elements as you hunt down the scientists, RDUs, and anything you haven't smashed to the ground yet. Then come the vehicle racing levels...
Killer7 is notoriously hard to describe. Much of the game is a Rail Shooter, except that you can freely move back and forth along the rails, which branch off in different directions, and the camera is in the third person when you're not aiming at things. Along with shooting enemies, there's also adventure and puzzle elements added as well that make it much like a Survival Horror game. The story, meanwhile, deals with a mix of foreign politics, government conspiracies, uber-powerful assassins, supernatural living weapons and just balls-out incomprehensible, nightmarish insanity.
The now-famous Warcraft map/mod Defense of the Ancients: All-Stars was this, though it was actually preceded byAeon of Strife, a map for StarCraft. Its popularity spawned a genre variously known as Multiplayer Online Battle Arena games (MOBAs) or Action Real-Time Strategy games (ARTS). Many of these games are called DOTA-clones due to their similarity to the original Defense of the Ancients game, right down to copying the map out of it (and frequently, including many heroes which are extremely similar to the heroes present in the original game), but the genre has since expanded to include games such as Awesomenauts, which are certainly in the same genre and yet decidedly not clones.
Deus Ex director Warren Spector said in an analysis of the game, "Conceptually, Deus Ex is a genre-busting game (which really endeared us to the marketing guys) — part immersive simulation, part role-playing game, part first-person shooter, part adventure game."
In keeping with Simogo's motto of not making games of a specific genre if doing so would impede the gaming experience itself, Year Walk can most accurately be described as a point-and-click first-person Survival Horror and adventure iOS side-scroller puzzle game.
Other elements of this include that there are no Action RPG elements like Devil May Cry or Bayonetta have, (like getting new weapons or collecting stuff like a Heart Container), nor is there a upgrade of stats. Asura's stats instead change depending on the episode.
One can also add in Fighting Game thanks to a coming DLC that pits Asura against Ryu, complete with the health bar, super gauge and Ultra gauge from Street Fighter IV (although in Asura's case, the latter two are replaced by his Burst and Unlimited Mode Gauges).
A review has pointed out that while this might not really be considered a "game," but as a multimedia experience, it is a memorable one.
Guilty Gear 2: Overture is part hack-and-slash and part single-player "massive online battle arena" (think League of Legends, which came out the same year) with a button to give the player characters race car controls, and a separate screen to control your MOBA units with a real-time strategy interface. Keep in mind the rest of the franchise is your bog-standard Fighting Game series.
Pixel Junk Nom Nom Galaxy is an odd game that combines elements of tower defense, buisness simulation, and farming, all layed with a Terraria-style sandbox-survival gameplay.
In terms of gameplay, Kingdom Hearts is a pretty standard hack and slash (though Chain of Memories did include some kind of weird card game sysstem on top of it somehow), but in terms of plot it's as genre defying as it is confusion. The hero travels through multiple worlds on a spaceship visiting and helping local populace which sounds pretty straight sci-fi, but he also knows magic and wields a giant key like a sword. There's no advance technology despite the spaceship except when there is like in the Tron worlds. Artificial life is present and is created both scientifically and via magic. It doesn't just stop at science fantasy though. The hero fights the evil in peoples hearts which can manifest as cute little creatures a foot tall, to complete eldritch abominations, to weird armored...things? There's some solid horror present with the sort of things that can be done to a person in this universe. Some games end in friendship conquers all type plots while others are absolute tragedies. Given the fact that by very concept the story is about following the plot of multiple Disney movies it inevitably is going to pull from a very wide range of themes, genres and aesthetics leaving one with something that doesn't seem to fit into any category even when it uses completely original characters and settings.