Valve's stand-alone sequel to the popular Warcraft III mod Defense Of The Ancients. Valve had hired Icefrog (One of the game's original developers) and have been working on a commercial sequel/remake of a sort called DotA 2. It was recreated on the Source engine with all-new graphics and UI. It was released in July 2013 after a lengthy closed beta. Recent updates about DOTA 2 can be seen here.
Dota 2 provides examples of the following tropes:
Ascended Glitch: Several quirks of the Warcraft III engine were intentionally replicated, and several quirks of the early beta have been left intact as well:
Though integral to the game for years, "denying" allied creeps (killing them to deny the enemy the cash reward) was originally a glitch.
Creep stacking is a method where a player draws the aggression of neutral creeps to make another stack spawn at the minute mark, when all empty camps will respawn. Though originally a glitch, this is such an integral part of DotA that removing it was unthinkable.
Although since removed, Valve at one point stated that the technique known as "fountain hooking" would be left in the game. Fountain hooking refers to aggressively teleporting or dragging an enemy into their opponent's fountain, where the high damage will likely assure an Instant Kill. While it's most well known with Pudge and Chen, it was possible with a small handful of other heroes as well.
The original Dota mod had three factions, including a neutral side, and normally defaults to allowing the Dire and Radiant to only pick from their hero pools and the neutrals. Completely open picking became ubiquitous in later versions, however, so the formerly neutral pool has been integrated into the Dire and Radiant sides. Thus there are True Neutral characters like Sand King on the Dire, and mercenaries like Bounty Hunter on the Radiant.
Backstories of various characters have been changed, in order to avoid references to Frozen Throne, since Dota is set in a separate universe, and Blizzard owns the copyrights to all elements of the Warcraft games, many of which were incorporated into the original Dota. However, even characters whose backstories have been radically changed are still on whichever side they were on in the original Dota. So, while Centaur Warchief is a heroic saviour fighting for the Sentinel in Dota 1, his equivalent, Centaur Warrunner, is simply a Blood Knight on the side of the Radiant in Dota 2.
Call a Smeerp a "Rabbit": Quite a few characters, mostly with Sniper and the archers; Sniper refers to arrows as "feather bullets" and Windrunner refers to Sniper's bullets in turn as "tiny featherless arrows"
Captain Ersatz: Due to certain heroes from the original mod being named directly after Blizzard-trademarked characters or races, some heroes had to be renamed.
Cast of Snowflakes: Every character has unique appearances, abilities, backstories, and extensive responses to certain events. All of them are fill in very different niches in gameplay and team composition, to the point where several heroes' schtick cannot be replicated by another.
Magnus can grab the entire enemy team into a single area and disable all of them with Reverse Polarity before Sven walks up and uses his high damage and Cleave to dice them all up in seconds while using storm hammer a smaller aoe stun to give them more time to beat on their victims and Magnus's Empower gives both of them more damage and Cleave.
Ursa has effectively neigh-infinite potential damage due to being able to do more damage every attack using Fury Swipes, and uses this to kill Roshan at an early stage of the game, however he will usually not last long enough without lifesteal effects which, other than for the somewhat expensive Vladmir's Offering, not work with Fury Swipes. Enter Skeleton King and his Vampiric Aura which grants all nearby Allies Lifesteal.
Huskar has an ability that deals 50% of the opponent's Heatlh in damage, Necrolyte can deal damage based on how much Health his target is missing. Targets of this combination tend to die.
Tiny's ultimate makes him bigger and stronger for each level put into it, but with the tradeoff that it reduces his attack speed permanently. Enter Wisp and its Overcharge ability that gives Tiny just enough attack speed to effectively ignore the attack speed loss.
Complete Immortality: A number of the characters (Keeper, Enigma, Chaos Knight, and Wisp) are Fundamentals: beings from the beginning of reality that are ageless and impossible to truly kill. The Radiant and the Dire are also Fundamentals, ones that were cast out by the others for constantly feuding.
Continuity Reboot: The original Dota never had much of a story past minor hero and items descriptions, and for the most of it used lore already established in Warcraft as a base. With the sequel being developed by Valve, they couldn't obviously use anything relating to Blizzard products. This gave them the chance to completely clean the slate and create their own fantasy world, giving all the heroes completely new and original backstories, though still using the original Dota heroes as a base.
Death of a Thousand Cuts: Many heroes have area-of-effect spells that don't do very much damage to single targets at all, or have auras that don't do a lot by themselves. The difference comes when you stack those spells and auras with those of the other four players on your team, which can quickly grind down even the hardest carries in the game under the right situation. That makes tactics very important to players.
Dem Bones: The Dire has quite a few undead heroes.
The Dev Team Thinks of Everything: Valve had every voice actor do a line for purchasing an Aghanim's Scepter, even heroes whose ulti couldn't be upgraded. Loads of heroes have had ultimate upgrades added since the lines were recorded.
Evil Laugh: Very prominent. Almost every hero has a response of this sort to killing an enemy hero. Oddly, in this game it doesn't produce any Narm feelings, because whoever just scored a kill will usually feel like a badass, so if you get the laugh response it just makes the experience better.
Better watch your back, because Bristleback is back! (kill me).
Homing Boulders: If a hero buys an item that gives them True Strike, which ensures that every attack will hit, it's possible for an autoattack to change direction in midair and fly across the map if the hero it was targeted on teleports away. This is especially ridiculous with characters like Sniper, whose bullets can spin right around in midair to chase their target or Tiny's Toss, where the projectile is an often unwilling enemy who kindly redierects his course at Tiny's target. It also gets absolutely ridiculous with skills such as Huskar's Life Break, where Huskar actually changes direction mid-air if his target blinks away, even if the target blinks behind Huskar.
I Shall Taunt You: Certain characters have specific, mocking lines when killing other heroes. Some even have dedicated taunt animations that can be executed on command if you own the item in your backpack. Axe does this too, to get people to attack him so he can counter-helix.
More than Mind Control: Non-heroes exposed to Direstone or Radiant ore quickly become warped by it and turned into creeps. This is ultimately reversible, though not without extreme effort.
Mythology Gag: If you look closely at the icon for item recipes, the icon in the middle is the symbol of the Combine from Half-Life 2.
Stealth Pun: ...Because you use recipes to COMBINE items.
No Experience Points for Medic: You only get assist credit (and gold) if you damage the slain enemy. This is why certain supports (like Omniknight) tend to not have great scores since they lack easy damage spells to pick assists up.
No Sell: One of the biggest mechanics of the game's meta-strategy is that some heroes are complete hard counters to others (such as Omniknight's Repel being able to completely nullify the effects of Slardar's Amplify Damage and many of Spirit Breaker's abilities, but Repel itself able to be purged by a Diffusal Blade), so choosing the correct lineup or item build against the other team can result in this. Again, rewarding good decision makings: turn the tide of the battles even when you are behind, if you are smarter than your foes.
Our Dwarves Are Different: While not outright stated, the Keen (Sniper, Tinker, Clockwerk, Gryocopter, and the smaller half of Alchemist) share similarities with Dwarves. Most are incredibly smart and sport facial hair, and are all very small in stature.
Race Against the Clock: If both teams go all-in on a push into the enemy base, it usually turns into this. Known as a "base race" in the community.
Race Lift: Tresdin the Legion Commander. Originally a white man in Dota 1, they are now a black woman. Doesn't mean she lost any of the racism towards non-humans or any of the bravado. Considering Skeleton King's remake into Wraith King, she's the strongest contender for Ostarion's old title of "Manliest Hero in Dota who lacks testicles."
Random Drops: Incorporated using a system similar to Team Fortress 2, in that only cosmetic items drop.
Revenue Enhancing Devices: Despite the fact that the game is completely play-for-free from the get-go, and you play as every hero from the start, the online store still manages to have a ridiculous amount of purchasable-with-real-money content. With the exception of tournament tickets (which allow you to spectate international tournaments from in-game) though, all of these store items are only cosmetic in nature, a vast number of them can be obtained through Random Drop as above (with even some only being available through drop and not through the store), and none of the availability of the game itself is locked away. An exception to the tournament ticket rule goes to the annual "The International" tournament held by Valve. You can watch the in-game matches for free, and Valve makes money by selling "See it live" tickets and (for the 2013 tourney) the Compendium which is $10 for at least $35 worth of content and a promise for more as more Compendiums are bought.
Beating the newly resurrected Wraith King shows the words YOU DEFEATED.
Schizo Tech: Several of the Keen (ie, the Gnome analogues) have incredibly advanced technology, Tinker even having lasers, rockets, and automonous robots. They exist alongside and are routinely beaten by people using arrows and swords. However, Gryocopter's backstory mentions finding an "incomplete schematic for a Gyrocopter, the world’s first manned, non-magical flying device". So, while technology, with the help of magic, is incredibly advanced, pure technology is mostly inept.
Socketed Equipment: As of November 2013, cosmetic items now can be socketed, for gems which give special cosmetic effects.
Standard Status Effects: Poison damage, paralysis, stuns, slows, and silences are invaluable in teamfights. Several heroes (Venomancer, Viper, Silencer, Bane, Lich, and Spirit Breaker, to name a few) are themed entirely around a specific status effect.
Suffers Newbies Poorly: As with many other games in the MOBA genre, gameplay is extremely serious business, and new players are often subjected to an incredible amount of vitriol. The developers have tried to alleviate some of this by introducing a tutorial mode, but it's a long and steep learning curve no matter how the game is played.
Talking Is a Free Action: Characters regularly banter with each other. Heroes will comment on loads of events, including buying a specific item, calling misses, killing certain other heroes, meeting certain allied heroes, getting a cosmetic item at the end of a game, and getting banned during the ban/pick process in Captain's Mode. Taken to ludicrous extremes with Storm Spirit, who takes this up to Lull Destruction.
Talking to Himself: Despite having well over a hundred different heroes, there are scarcely more than ten or twenty voice actors to give them all voices. While some of these are fairly obvious (Anti-Mage, Beastmaster, Necrolyte and Warlock are all voiced by Sam A. Mowry, and sound like the same person at different ages), quite a few are very surprising (Crystal Maiden, Drow Ranger, Enchantress, Mirana, Phantom Assassin, Spectre, and Vengeful Spirit are all voiced by Gin Hammond, and Timbersaw, Bristleback, Skywrath Mage, and Abaddon are all voiced by TJ Ramini).
Touched by Vorlons: Several characters have abilities conferred by beings greater than themselves.
Unexplained Accent: A good majority of the heroes are outfitted with various accents despite not being in the real world.
Anti Mage, Invoker, and seemingly Axe speak with light English accents. Pudge speaks with a more thick urban English accent, as does Bristleback.
Skywrath Mage, Vengeful Spirit, and Lycan seems to speak with a Transylvanian accent.
Mirana speaks with a light Greek accent.
Meepo's accent sounds somewhat like a typical Brooklyn accent.
Luna has a very thick Irish accent.
Death Prophet has a very thick French accent, while Phantom Assassin has a more subtle one, perhaps French-Canadian.
Slark has what sounds like an Australian accent.
Through her echoing voice, Medusa sounds like she has a high class English accent, or an older American accent, like one from the 1940's -1950's.
Chaos Knight has a deep voice, but he appears to have a German accent.
Dazzle has a Mali accent.
Magnus has an Ethiopian accent.
Witch Doctor has a Rastafarian-type accent.
Bloodseeker sounds like he has a Central American Accent to go with his 'Sacrificial Tribal' Theme.
Shadow Shaman has a Persian accent.
Sven and Tusk have Swedish accents. Sven sounds more like your typical Viking where Tusk sounds more like a Modern Swedish Accent.
Brewmaster and Juggernaut have Japanese accents.
Lone Druid has a Scottish Accent.
Updated Re-release: The game is more or less a direct clone of the original Defense Of The Ancients All Stars map from Warcraft III, but has a new engine, brand new graphics and a modern interface. Several characters work differently because of the new engine, as the old Warcraft III engine put restrictions on certain spells. Rubick can steal transformation skills (most notably Elder Dragon Form and Shapeshift), and Luna's Moon Glaives work differently. Visage is probably the greatest example of this. Three of his four skills were changed from the original.
What the Hell, Player?: Attempt repeatedly to use an ability when it's on cooldown or you don't have enough mana, and your hero will sound more and more agitated/annoyed with your rapid clicking. Troll Warlord especially hates it when you do that.