Odd or Even is a classic summer road trip game that, while usually played by two, can be played by as many as is desired. This will probably sound barbaric, but I swear it's good, clean fun.
Party one begins by grasping a pinch of party two's leg hair. The next step can be slow, with an evil stare, or quick and painless: the victim's leg hairs are ripped out. He's discouraged from screaming as the searing pain of hair torn from its roots takes hold of his body, already tingling from being cramped in the back seat of dad's Dodge, although it's certainly not forbidden. He must immediately guess: odd or even. Once he has made his final guess, the hairs torn out are counted. Should his guess be correct, he is the "winner" of the round, and slugs the other party. Should he be wrong, however, he is slugged himself, and bears the burden of double-pain during the round.
Play continues until neither party has any leg hair left, or dad threatens to turn the car around, whichever comes first. When you get bored of travel bingo and battleship, odd or even is definitely the way to go. | 
