Apple - Safari
My primary Mac is an iBook (12" PB is starting to tempt me!). The 1024x768 display is pretty small. I'd use the Full Screen view of Firefox or IE if Safari supported it, but it doesn't. Alas, even Firefox on the Mac is lacking -- the F11 key is used by the MacOS and thus there's no keyboard shortcut for Firefox Full Screen mode.
The next best thing is to hide the address bar. There is a shortcut key for that: Cmd-|. It's conveniently located above the enter key, but to get it you need to type the shift key (the default is \).
The oddity occurs if you have Safari debugging turned on. Then Cmd-\ (same key but without the shift) brings up an interesting page debug menu. I don't actually use the Debug menu much, so I may disable it and see what Cmd-| does then.