A fire escape ladder, a guitar box, my old college books, an old lectern filled with construction/doodle paper and supplies, and my collection of Gameboy/GBA/DS games. Oh, and I also have some various gaming related stuff down there as well. I have my spare controllers, and all my cables down there too.
And yes, I have a collapsible ladder under my bed. I'm sorry but in case of a fire that I can't get downstairs from, I think I would rather knock the screen off my window and just fall a story and a half, rather than fight with the ladder and the fire.