Settlers of Catan. Yes, great gateway game but for some reason I don't care about playing it. Maybe because I've never won, (yes, something as silly as that affects my judgement). Seems like the only way to get ahead is being a jerk and cutting off another persons growth, especially in a 4 player game (have not played with the 5-6 player expansion).
My GM refuses to play Apples to Apples, which I love to tease him about.