Dungeon Shop

"Screw the guy who blasts through the undead scourge and penetrates the deepest levels of the sewers to save the president's daughter. We want to know about the guy who's so badass he beat us there and set up an item shop and shooting gallery. And hey, if he's so good at getting around, why doesn't he save the president's goddamn daughter, huh? And, couldn't he find an area with a wider customer base?"

- Cracked.com's 6 Video Game Gimmicks That Need To Die

In videogame dungeons, in the midst of Everything Trying to Kill You, one may find shops selling all sorts of items, varying from not actually useful to somewhat useful to absolutely necessary. If the shopkeepers are standard NPC types, there is the Fridge Logic question of how they made their way down there in the first place without getting slaughtered, and what shortcuts they are using to bring supplies in (as they often will restock after a while). The shopkeepers need not be Muggles, though; they might be friendly versions of the local monsters. See Intrepid Merchant.

Shoplift and Die, naturally.

For the inverse, see Dungeon Town.

Platform Games

 * Many of the shops hidden in the ruins of La-Mulana are hidden behind walls. Some just sell ammo, but others (including one Guide Dang It example) sell vital and otherwise unobtainable Plot Coupons, though they don't come cheap. The shopkeepers tend to be undead, and say that you're the first customer in hundreds of years.
 * The dungeons of Spelunky have, besides the ordinary emporiums, gambling parlors, kissing booths and the super-secret Black Market. The shopkeepers are tough and well-armed, as players may find out the painful way, meaning that it is actually reasonable for them to have made it through the dungeons. That still doesn't explain why they feel the need to serve the vast customer base that typically appears miles underground. Or why they don't just grab the gold lying around themselves.
 * Hammer sets up shops like this in the Castlevania games. Seeing as how he's a former military man and is seen with a bazooka at one point, it's fair to assume he can take care of himself.
 * The Castlevania (Nintendo 64) games have a shop master that appears with the activation of a scroll. Just don't get TOO greedy...
 * Justified in Symphony of the Night. The shopkeeper is Dracula's librarian and an old friend to Alucard. Note that he won't help Richter at all.
 * In Harmony of Dissonance, a wandering merchant got lost in the castle,and so he set up shop there. No idea who the rest of his customer base is, though.
 * The merchant in Prehistorik Man sets up shop in pretty much any non-friendly territory...though he'd not get close to the haunted Dinosaur Graveyard.

Role Playing Games

 * Torchlight has them. Possibly justified by the fact that they're travelling goblin (who might get a free pass from some of the dungeon's inhabitants) merchants.
 * Wild Arms 5 has them in little jack-in-the-boxes.
 * Santa shows up in Star Ocean the Second Story in the Bonus Dungeon and sells you stuff.
 * I'm sorry, what? Are we talking the same Santa I'm thinking of?
 * The Camp Gay brothers in Shadow Hearts: Covenant show up almost everywhere. They lampshade it in the Neam Ruins; when you talk to them, they bitch about having had to go through all the puzzles to get that far and demand you make it up to them by buying their goods. (They also offer you a ride out in their van.)
 * Most Roguelike games have sections of dungeons that contain items for purchase. Try to leave their store without paying, however, and you'll face some very nasty consequences.
 * Played with in Desktop Dungeons, which has single-item shops. "After you make your purchase, the mysterious shop mysteriously disappears. Mysteriously."
 * The Kecleon shops in the Pokémon Mystery Dungeon Games. Possibly justified by the fact that they're always at ridiculously high levels and will most likely kick your ass if you steal from them.
 * Brax the Salesdemon from Dungeons of Dredmor almost makes sense. Being a demon, he can summon Debt Collectors (more demons), which explains why monsters don't dare attack him. Also, most civilians probably wouldn't buy merchandise from a demon, even one with a suit, so he just markets his stuff for adventurers who find his shops.
 * One long dungeon in the first Phantasy Star game contains... a bakery, in which you must buy cakes and return them to town to progress the story.
 * One dungeon in Shining Soul II is actually a house and storefront that you are asked to infiltrate by the Hub Town's storekeeper. The entire purpose of going there is to secret-shop so that the storeowner can compare prices and undermine her rival.
 * Atelier has you play as one of these shopkeepers.
 * There are in-game examples in the Mana Khemia subseries: in 1, there's a student-run store in the Student Resource Center dungeon, and in 2, the person selling stat-boosting items is found in a dungeon. It's justified by the fact that at Al Revis, sending teens to face a dungeon full of monsters is a perfectly normal homework assignment, and anyone with so many stat boost items that they're selling them likely doesn't have to worry about random encounter monsters.
 * The Catgirl Koma in Super Robot Taisen: Endless Frontier games has a habit of setting up shops in the middle of dungeons, although depending on her mood and current employer, she might want to fight you first. Justified in the first game due to her being a competent fighter as stated above and in the second game, she's travelling with you. She almost gets left behind after temporarily seperating from the rest of the party to peddle her wares when the Load-Bearing Boss's defeat takes effect though.
 * These are a staple of the Final Fantasy series, first seen in Final Fantasy II under a waterfall in the Jade Palace, and last used in Final Fantasy XII in the Necrohol of Nabudis - where one of the monsters is a shopkeeper. Final Fantasy XIII replaces this with access terminals to online shops. Some of the places those terminals show up, though, is rather strange.
 * Justified in Okami. The only shops in dungeons are run by monsters. (And yet, they still sell the holy paraphernalia Ammy needs to do her job...)
 * Neko from Secret of Mana would sometimes pop up in dangerous places, like a forest infested with monsters.
 * Playfully avoided in Jade Empire: the main character has (from a very early point in the game) a personal merchant spirit that constantly follows him/her from the spirit world, making sure that you will always have access to a shop-full of magical goodies wherever you are.
 * In Xenogears, a couple of dungeons had shops run by Fixbots; one could choose "I don't trust you" when talking to them, leading to a fight...but doing so would (obviously) remove the shop, seeing as you just killed the owner.
 * The first Paper Mario game has a bored storeroom guard in Bowser's Castle that will gladly sell Mario his inventory (at heavily inflated prices, of course).
 * In the second game's Pit of 100 Trials, there is a random chance of a shopkeeper appearing every 10 floors.
 * Mario & Luigi: Partners In Time has Monty Mole's Mole Mart, which is not just in a dungeon, but hidden in a dungeon. And Fawful's Bean'n'Badge, which is in the castle sewers (counts as a dungeon, since they're swarming with Goombas).
 * Don't forget Hinopio's shop in Barrel Volcano in Super Mario RPG!!
 * Played with in Dragon Age Origins. During the "A Paragon of Her Kind" quest, the PC will encounter a dwarf named Ruck in the Giant Spider-infested Ortan Thaig. Ruck is deliberately hiding out in the ruins of the thaig and has become tainted from eating darkspawn flesh. Provided you don't kill him, Ruck will trade you items that he scavenged from the ruins.
 * Then in the Very Definitely Final Dungeon, literally two rooms before the final boss, you find Sandal, standing hip deep in Darkspawn corpses and with his father's full inventory available for you to load up. The game allows you to express your disbelief and demand an explanation, which is of course just answered with "Enchantment!"
 * The Awakening Expansion Pack features yet another salesman in a darkspawn lair. At least this time, the guy explains that he has an agreement with them to bring them supplies. You can convince him to move his business to your castle instead.
 * Not only does Sandal do that again in the Dragon Age II endgame, but he also helpfully hauls your own party storage chest all the way to the final dungeon.
 * Happens three times in The Legend of Dragoon: A (justified) merchant in Hellena Prison and the four brothers Primero, Tercero, Segundo and Quarto. The first two are met in a frozen glacier, the latter in an abandoned, mystical ruin.
 * Breath of Fire: Dragon Quarter has the three puppet ladies, who sell up items, weapons and the like in areas where no normal citizen would be able to even reach. They also move faster than the player's party, somehow...
 * Legacy of the Wizard has over three dozen shops in the dungeon, not counting Trauma Inns. However, most of what they sell can be obtained free if you know where to look.
 * The last merchant in Nox sits rather uncomfortably on the edge between the Land of the Dead and the Dismal Swamp, within running distance of the Necromancers' fortress.
 * There's only one of these shopkeepers in The Haunted Ruins, but she keeps showing up lower and lower down. As she does, her sprite slowly shifts (and she keeps insisting that the change is all in your head.)

Shoot'Em Up

 * Forgotten Worlds presents us with Sylphie, the Arms Dealer with the shop which literally comes out of the ceilings/floors within enemy areas. One wonders how did she set up her shops that way...
 * Deus Ex Human Revolution has a LIMB clinic semi-hidden within The Very Definitely Final Dungeon. Mostly Justified because the area only became a "dungeon" when an event caused most of the population there to go insane, and the shopkeeper managed to barricade herself. Transactions are all computer-based, which explains why the shopkeeper simply can't give you free merchandise. Still, it does come off as a bit silly.

Third-Person Shooter

 * As alluded to in the Cracked.com quote, the pirate merchant from Resident Evil 4.
 * Global Agenda. Why are there people standing out in the middle of the desert? Right near colonies of respawning robots? Alone? We have no damn clue.
 * Also, why do they give you random stuff? Sure, I suppose she has a gun. But she needs that.