A four string guitar that is several octaves lower than a guitar. It is more commonly played with your fingers than a pick. Also, bassers (more commonly known as bassists) are usually the weird ones in the band.
They are also usually quieter and calmer than guitarists and drummers. And can therefore usually be pushed around more easily.
Guitarist Chick: Let me straighten your ridiculously curly hair!
Basser Dude: NO!
Guitarist Chick: Pleeeeease...
Basser Dude: Okay, fine.