OS X and wallpaper
This is a really trivial thing, but it’s so nice! You can separately set the image, scaling, rotation etc for the wallpaper on each monitor in a multi-monitor setup. I’m cheap, so my monitors are different aspect rations. The main monitor is a fairly nice widescreen LCD. The secondary monitor is a 4:3 CRT. This means that wallpapers need to be setup differently to look nice on the two screens.
Yes, I realize this is super trivial. Most of the time, I can’t even see my wallpaper. Regardless, it’s nice when things work so nicely. No more stitching images together in MS Paint!