CONFAB
Confab is a conversation-based blank-card game for any number of players; ideally two. It was idly invented for a prize in Round One of blognomic, and has been polished slightly for more-than-two-player games since.

Rules
Get a load of blank cards; at least ten per person. Everyone then scribbles arbitrary conversational sentences ("Hello." "How are you?" "Yes." "No." "You're very tall.") onto the cards, until they're all covered.
Shuffle them all together, deal five to each person and leave a face-down draw pile.
Taking turns, players must either play a card from their hand that follows conversationally from the previous card (or opens the conversation, if they're the first to play), or - if they can't go - draw a new card from the draw pile.
If playing with more than three players, each card played should be directed at another person - he or she must take the next turn. (Generally speaking, answers to questions must be directed back to the questioner, but go with whatever makes sense in context.)
When a player passes, the previous player gets another go - they can treat the pass as a pause in conversation, if they like.
Resolve disputed plays via persuasive debate, or a simple vote. The first player to empty their hand wins.