My guildies and I have just started participating in something we've coined the Naked Dungeon Challenge. It's a fun way to kill some time and it's turning out to be surprisingly competitive and entertaining.
Basically, you take off all your gear and start running through the dungeons, in order, starting with Ragefire Chasm, then Wailing Caverns, etc. You can use all class abilities, pets, etc., but you can only equip items that you find in the dungeons.
The tricky part is that everyone rolls Need on EVERYTHING, since you're competing against the other players. For example, a Boss drops a shield and you can't use shields? You still roll Need, because a shield you win is a shield your rivals can't equip!
(Crafting professions are technically allowed, but you can only use mats that you find in the dungeons. For example, Tailors will probably find it pretty hard to make themselves any low-level gear without access to Coarse Thread. ;D)
It quickly becomes a hilarious game of one-upmanship. You might get some lucky rolls off the start and get a weapon and chest armor, but then be unable to find any pants. Or a staff will drop, and the non-staff wielders will cheer and celebrate if they manage to keep it out of the mage's hands. Meanwhile, white and grey items skyrocket in value, since you don't have to roll for them - those elusive gloves or pants might end up being "vendor trash" if RNG isn't on your side!
Incidentally, the sadistic glee that comes from stealing away someone's much-desired, precious pants and destroying them before their eyes is priceless. ;)
Finally, for added randomness and silliness, you could also use the rule that you absolutely HAVE to wear the highest item level equipment you find. This makes it especially funny when you have a nice blue-quality piece of gear from a previous dungeon, and then find a horrendous green item - or even a white or grey item - for the same slot that is a higher item level. This happened to me - I went from having a nice 2-hand sword to using a silly lantern off-hand (with no main-hand weapon).
Oh, and one rule - you're not allowed to go back and "farm" dungeons alone, since that removes the competitive aspect of the game! You're supposed to end up using ugly and awful gear. That's the whole point! :D
If you do try this challenge with some guildies/friends, I recommend taking "post-game" screenshots at the end of every dungeon, showing everyone's ridiculous ensembles. It's quite funny to see the gear radically change between dungeons, and who got lucky on a particular run, and who continues to have no luck at all.
Here's some shots of our group (Paladin, Mage and Death Knight) after Ragefire Chasm, Wailing Caverns, Shadowfang Keep and Blackfathom Deeps. To get an idea of the gear, I've included what I was using at the end of each dungeon. You'll notice that the Paladin went three dungeons before getting pants, and after four dungeons, I still don't have any chest armor. :| Damn you, RNG!
Oggleflint's Inspirer, Aboriginal Cape, Grizzly Pants of the Monkey
Gleaming Claymore of the Bear, Serpent's Shoulders, Greenweave Cloak of Stamina, Grizzly Pants of the Monkey, Ritual Sandals of Spirit
Seer's Mantle, Greenweave Cloak of Stamina, Eerie Stable Lantern, Buccaneer's Pants of the Owl, Ritual Sandals of Spirit, Silverlaine's Family Seal
Seer's Mantle, Greenweave Cloak of Stamina, Eerie Stable Lantern, Moss Cinch, Buccaneer's Pants of the Owl, Tough Leather Boots, Silverlaine's Family Seal