Go down in the dungeon. Kill everything you meet. Backstab your friends and steal their stuff. Grab the treasure and run.
Admit it. You love it.
Munchkin is the mega-hit card game about dungeon adventure . . . with none of that stupid roleplaying stuff. You and your friends compete to kill monsters and grab magic items. Don the Horny Helmet and the Boots of Butt-Kicking. Wield the Staff of Napalm . . . or maybe the Chainsaw of Bloody Dismemberment. Start by slaughtering the Potted Plant and the Drooling Slime, and work your way up to the Plutonium Dragon!
Start with the Munchkin Deluxe Edition. When you want more variety, there are lots of supplements you can add . . . more silly monsters to kill, more great treasures to find!