A good portion of the game's items, skills, and descriptions are direct nods to games, movies, and franchises of various media. Mixed
The level-up screen says things like "Your princess is in another castle" (misquoting Super Mario Bros.), "It is dangerous to go alone! Take this" (The Legend of Zelda), "Power Level 1,370" (Dragon Ball Z), "Drinking from the Fire Hose", "Conan the Librarian" (UHF references, the latter a parody of Conan the Barbarian), and "The Blue Thunder of Furinkan High" (Kuno's self proclaimed moniker in Ranma ˝) just to name a few.
Almost all of the game's Steam Achievements are shout-outs. See the wiki for details.
To Super Mario Bros. (in the fungi, there's the Plumber's Agaric which provides a strength buff), and The Prince ("A regal mushroom better feared than loved.").
If you try to shoplift, Brax's enforcer demons will tell you to Respect Mah Authoritahnote Getting killed by these enforcer demons will give you the achievement of the same name (South Park). If you talk to Brax without shoplifting, he'll tell you to "Buy something will ya?" (The Legend of Zelda)
The Undead Aethernaut is based on the Vashta Narada (Doctor Who); it's noted that "Ground Control really lost this one", along with its late-game spriteswaps being named "Major Tom" and "Aether Oddity" (David Bowie).
A comment between the effects of Gog's Tactical Pyre and Infernal Torus wonders, - <!-- but does it blend? --> A few lines below that, under the effect Flamefield 2, a developer adds the line, - <!— Because you're worth it. —> from L'Oréal.
Anime / Manga
One of the higher-tier pieces of headgear you can find is a red, wide-brimmed Vampire Hunter's Hat (identical to the hat worn by the protagonist of Hellsing), which according to the tooltip "isn't really suited for vampire hunting, but what can you expect out of someone who thinks that spelling 'DRACULA' backwards is a good way to hide their identity?"
The achievement "The Humanoid Typhoon" is an obvious shout out to Vash's moniker in Trigun.
The Archaeology skill tree is loaded with Indiana Jones references, including a skill called "It Belongs In A Museum". You even start out equipped with a sufficiently Nice Hat. Additionally, the description of first Egyptian Magic skill, "Glyph of the Asp," asks, "Why did it have to be snakes?"
One demi-artifact armor piece is a Mad Max-esque black leather jacket with one-sleeve. It forms part of the crafting recipe for the Magical Badass Jacket, whose description is "Do you feel magic? Well do ya, punk?" (Dirty Harry)
The Lundi enemy is a complete shoutout to Lumbergh of Office Space in both flavor text and ability to inflict The Mondays on the player.
One of the possible readable books that serve as warnings or useless info is named A Tome of Fire or Ice.
Wizardlands introduces a new alloy (that Banksters start with a few samples of) called Rearden Metal (Atlas Shrugged) ...which is really "only" good for attaching a powerful existential attack brand to your weapons. Thing is, perhaps because there was no government or other neutral oversight, the stuff has a tendency to explode. Generally when exposed to enough sunlight. Or oxygen. Also worth noting is that instead of the usual alchemical symbols of the more normal metals, Rearden ingots are stamped with a dollar sign—the sign that Galt traces in space at the very close of Atlas Shrugged as the sigil of the Gulch.
Conan the Barbarian: The Rage skill tree is full of pledges in the general direction of "For Crom!"
The Mobile Carrot class of enemy is described as "a man-eating carrot, not to be confused with a man eating carrot" — evidently a reference to an Ambiguous Syntax moment in GrailQuest.
The Crown of Yellow is a magic-oriented headgear item with origins from The King in Yellow. The book itself is among the many magic tomes you can find and use. (Apparently "the beginning is a little dull", if the tooltip's to be believed.)
Brax and the Dread Collectors are characters in Craig Shaw Gardner's Ebenezum and Wuntvor series of comic fantasy novels.
The Prodigy: The description for "Pyrokinesis" (Psionics): "You're a firestarter, a terrific firestarter."
Two abilities in the Viking Wizardry tree reference the Rhapsody of Fire songs Triumph For My Magic Steel and Unholy Warcry. The references continue in Conquest of the Wizardlands with the Emerald Sword: "Forged by the last Winged Unicorn; wielded by the Swordmaster to defeat ultimate evil, this sword has found its way to YOU." Said expansion also has an achievement named Magic of the Wizard's Hangover (referencing Magic of the Wizard's Dream, a.k.a. The One WithChristopher Lee Singing).
Enter a pocket gate dimension and listen to the music. Does it sound similar to End of Time?
With the Wizardlands expansion, you can encrust your armor with pieces of meat. The name given to this? Gaga's Glaze.
Several of the second floor's tombs bear the names of the default party members from Darklands.
Dawn of War: Blaze of Glory effect: You can not burn, for your heart is already ablaze with passion. If you die this day you will die in glory, but NO! you will not die this day! It is your enemies who will taste death and defeat! You are a CLOCKWORK KNIGHT! Long live the Queen! Glory to THE EMPIRE!
The original title screen, the status bar that's a close-up of your character's head and gets progressively more battered and bloodied when injured, and the graphic design of Floor 3 are all shout outs to Doom.
One of the armours originates from Doom, while equipping a helmet based off Quake along with it, gives you a "Realms of the Id" achievement.
Fellow indie game Dwarf Fortress gets tons of them. The biggest might be the ever-present ludicrously bizarre names randomly generated for all places and artifacts, one of Dwarf Fortress' famous traits.
The description for the highest difficulty setting is the official DF motto "Losing is Fun!"
The description for the "Shoddy Dwarven IED" trap reads "This is a sub-par Dwarven IED design. All craftsdwarfship is pretty lousy, actually."
The Plump Helmet is named for the food crop mushroom grown by dwarves in Dwarf Fortress, and its description reads "This helmet was crafted by dwarven smiths in ages long past from the weapons cast down by the dying goblins foolish enough to attack their undermountain fortress," a nod to the common strategy of salvaging metal from weapons dropped in goblin assaults.
The steel ingot description read "The steel ingot is a testament to the fact that you'd really rather be playing some other video game with a more finely honed crafting system. Oh well...". It is created by mixing chalk, coal and iron, which is similar to the way it is created in Dwarf Fortress (and indeed, in the real world).
The tooltip for Conflagratory resistance states that Asbestos Armor can cause, among other things, "Strange Moods" which are a random thing that can happen in Dwarf Fortress.
The description for bone crossbow bolts states "From the dark and icy north come these bolts carved by Dwarven bone-crafters from the still-twitching remains of fearsome undead skeletal elk", referencing the communityfortress Nist-Akath.
In the Conquest of the Wizardlands expansion, it's possible to craft a Dwarven Atom-smasher—a reference to the nickname given to drawbridges in DF.
There is a very subtle reference to Boatmurdered on the second floor with a grave that subtly references StarkRavingMad and the miasma he made during his turn in Boatmurdered.
One engraved artifact (as in, Dummied Out code) in the game's spell database is a note that says, "Skatha's Roots, added 2/6/2011. On the documentation is a picture of a programmer and an artist. The programmer is crying. The artist is laughing."
One of the types of booze is "Sewer Brew", which the Dwarves in Dwarf Fortress brew from ratweed.
If you happen to encounter a Game-Breaking Bug that makes the game crash (Most infamously the, fortunately fixed, save-game incompatibility of the latest patches), you get an achievement called "Suddenly the dungeon collapses!", which is the message you get when Nethack crashes.
The message log will sometimes mention, "You hear the chime of a cash register," an event possible in Nethack.
In the tech-based floor, the chests look suspiciously like a certain Portal puzzler's famousbox.
Thaumaturgic Conflux, a skill from the Ley Walker skill line that has a chance of increasing mana temporarily, has flavor text that references the Starcraft meme "power overwhelming".
A special diggle with name "Siegfried" may be found on the first floor. Anybody who's played Dungeon Crawl will recognize that as the name of a high level monster who has a habit of appearing on beginning floors, yet having the stats to easily dispatch a new character.
Wing Commander: The Monofiliment Sword is "favored by giant cat aliens."
Bea Arthur appears as an Amazonian Bumblebee Person named "Bee Arthur".
The descriptors for "New Bolt" and "Bolt Classic" should be more than a little reminiscent of one of Coca-Cola's gaffes.
Mao Zedong: One of the spell tomes you find is Lord Dredmor's Little Black Book. "It's filled with quotations from Lord Dredmor on all aspects of daily life." The Little Red Cookbook is another spell tome you can find and use.
The Aluminum Tube's description: "This is irrefutable evidence of Dredmor's nefarious plans." It was supposed to be a shout-out to Iraq's weapons of mass destruction, being used as one of ingredients for crafting Bolts of Mass Destruction. Sadly, Gameplay and Shout-Out Segregation meant that the recipe had to be changed.
The Root of T'char from Zalgo can be found and eaten. Doing so will kill you if you're not prepared.
Carl Sagan gets two items in reference to him: The Starry Orb and the Cloak of Sagan both make references to Sagan's 'billions and billions of stars'.