Children's birthday parties are fascinating places to watch human behavior at its most petty and brutal. My friend's 5-year-old daughter's party was tame in comparison to some I've seen -- until we got to musical chairs.
Musical chairs is a psychology experiment, conducted largely on the under-10 crowd, designed to separate the victims from the psychopaths. The point of the "game" is for a bunch of kids to circle around a row of chairs lined up back to back, but there aren't enough chairs for everyone, and one kid is left standing. That kid's job is to beat the crap out of the nearest kid and take his chair. The biggest, strongest kid wins.
I like games that give kids a solid lesson in evolutionary psychology while they're young.