I remember reading about MenuetOS years ago, apparently it's still available. It's an OS written entirely in Assembly and fits on a 3.5" floppy to boot from. It's not based on any particular pre-existing OS, but it has a web browser and some stuff, from what I can recall. The site has screenshots of people playing Quake and Doom, so it has some 3D capabilities.

Here's a link to its homepage.

http://www.menuetos.net/

I would like to try another os if I can find one, hehe. I have used litestep for a good while. Litestep is just a shell replacement though for a windows installation for example. Rather than using explorer.exe for the shell, it uses litestep.exe. Is there another OS that is similar to windows but faster with the same support for programs and such?