Alt-Tab Type Thing for Mac?

Hi, I would like to know if there is a key command in mac that works as well as alt tab in Windows.

I've heard about the cmd-tab and F9 etc, but what im looking for is one that works while you're using apps such as games.

On my windows partition I can play Oblivion and alt tab out of it to do something in windows and i would like to do the same sorta thing with mac. I have Quake 4 on my mac partition but cant seem to find any sort of similar function?

Cheers guys :D

the command/apple key + tab does exactly the same as alt tab in windows.

Apple + Tab works well, as does F9, which displays every open window at once

On leopard at least (maybe Tiger) the F3 key is used to display all the open windows at once and you can just click between them. Or yes as above command+tab is the same as alt+tab.
Cheers