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 (http://blognomic.com), and has been polished slightly for more-than-two-player games since.
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.
It sounds a bit of a throwaway game, but there's a good level of strategy and humour to it; the 'offensiveness' and 'defensiveness' of particular sentences, the vagueness of wild cards, the general effect of cartoon characters communicating via pre-written signboards. Language is a game, after all.
Available at:
http://kevan.org/games/confab.html