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.
Get a pile of blank cards, and deal out at least ten per person. Each player writes an arbitrary conversational sentence ("Hello." "How are you?" "Yes." "No." "You're very tall.") onto each card, until they're all covered.
Shuffle the cards together, deal five to each person and leave a face-down draw pile.
To start the game, the first player to call out a conversational opener from their hand gets to play that card. Taking turns from there, players must either play a card from their hand that follows conversationally from the previous card, 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.
Aleric : "Hello, Boris."
Boris : "What a lovely day, Aleric."
Aleric : "Yes, Boris."
Boris : "I say Colin, What time is it?"
Colin : [ he can't go, so he draws a card ]
Boris : "Aargh! Colin!"
Colin : "A hundred spiders, Boris?"
Aleric : "That doesn't make any sense."
Colis : "Yes it does, I was questioning his scream."
Aleric : "That seems a bit tenuous."
Boris: "It's fine by me."
Aleric : "Okay then."
Boris: "But enough of me, what about you? Aleric...?"
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 wildcards, the general effect of cartoon characters communicating via pre-written signboards.