Musical chairs is a well known party game that goes well with pretty much any party. You don't need much to play it and it's fun for both adults and children.
You have to set up one less chair then there are people playing. The game starts when the music starts. Players walk around the chairs (they are not allowed to stand still) and when the music stops, everyone has to sit down. Whoever is left without a chair is eliminated. You remove one chair and continue playing.
The game continues like this until only two players and one chair are left. Whoever is the first to sit down, is the winner!
Someone who isn't playing should be in charge of the music.
You can set up the chairs in two ways...
Arrange them in a circular or oval formation.
Randomly spread them across the room (but not too far apart).
A few fun ideas...
Office musical chairs.
Using office chairs that have wheels can make the whole experience even more fun. People can roll chairs away from one and other, they can spin them, roll away once they sit, it just adds a whole new element to the game.
Beanbag musical chairs.
Using beanbag chairs instead of regular wooden chairs makes the game a bit less dangerous and there might be some extra funny fights for the domination of that last beanbag (if it's big enough, you can almost shoot out a person when you sit on the opposite side:))
Wet musical chairs.
This is a version of musical chairs that requires a pool.
You can read more about wet musical chairs here.
Birthday party games