If the Black Pearl in JJPotC is a toy, then that's gotta be it for me. That thing made my jaw drop the first time I saw rocking back and forth. Spinning house on WoZ is up there, too. And can't forget good 'ol Rudy.
edit:
Quoted from mbaumle:The floating ball stage in Pinball Magic is pretty convincing. Really cool mechanism!
Ooh, and that one, too!