One of my favorite lenses is the Canon EF 16-35mm f/2.8L II USM that works great on both the 5D Mark II (full frame) and the 60D (cropped sensor). I don't use it everyday, but when I need it, nothing else will do.
I just read A Visual tour of Canon's 16-35mm f/2.8L II USM by Dave Powell on the Digital Photography School site. He includes lots of images from this lens. It's a great way to get a feel for its capabilities.