On the PS3, you could play Gran Turismo with up to five screens if you had five PS3s. I remember seeing the option to do that but never was able to try it myself and never saw anyone else do it. Pretty damn cool, a little funny but really cool. You don't see shit like this anymore really.
I did a little test playing Ocarina of Time across 3 monitors. It looked really awesome despite my monitors being all different sizes and different positions. I'd love to get two more of my main monitor to set up for a three monitor setup for some games, I think it'd be fun.