Started off with a Tamron 10-24mm, no complaints and it was nearly bomb proof! Then had a Canon 10-24mm, a great lens and still use it on my cropped sensor camera body.
Just upgraded to a Canon 11-24mm on a full frame body and it's stunning, wide, wide angle but without the distortion you get on a fisheye lens.
Always heard positive reports on a Tokina 11-16mm and the photos I've seen taken on one are always nice and sharp, never had the pleasure of using one though.