Munchkin 2: Unnatural Axe
Buy this firstBGG 6.43 from 7,629 ratings, the most-rated Munchkin expansion. Cards just mix into the base deck, and the set is also inside the Big Box.
Needs: Needs Munchkin or any other Munchkin set; it is not a standalone game.
Adds: 112 cards: the Orc race, monsters like the Hydrant and Tentacle Demon, plus Unnatural Axe, Spiked Codpiece and other items.