Scrabble. I enjoy playing, but in an informal, and definitely not too competative kind of way. When someone gets out the official book, and starts using loads of words that never see the light of day in normal discourse, it takes the edge right off the fun. It quickly becomes a test of who has remembered more of these obscure words.
The venerable Mrs Seed and I play our rule, that if you cannot actually say what the word means, you cannot have it. We cheat of course and make up meanings for stupid random groups of letters, but thats part of the fun, when we are well into our second bottle of wine.