[WSIG] Card game with coop/versus

Alright, so my friend introduced me to Munchkin not so long ago. It was very fun at first, but it gets repetitive, and I thought it would be fun to buy some expansions, until they get repetitive as well once I know the cards.

I'm looking for a game that is fun to play, that will still be fun to play even after I get to know the cards,, and which can be played in coop or versus (Because thats fun to stab my partners in the back).

Any recommendations?