I broke at least 6 Gamecube controllers, but that's because I stopped caring about their well-being after I got a warranty at Best Buy. I used the same $5 warranty for many brand new controllers, one of the controllers I returned was in at least a dozen pieces.
The best part is the poor wording of their old warranties, I got told once that I couldn't return my orange controller when the original receipt was for a black one, but the wording of the warranty was shitty, so I still got a replacement. :)
Other than GCN, I haven't broken any other controllers, although buttons have stopped working on my NES and Genesis controllers.
Currently playing: Uncharted: Drake's Fortune, NBA2k11, Metal Gear Solid, Picross 3d