byuu, the guy who gave use the most accurate SNES emulator bsnes and the MSU-1 enhancement chip to stream audio and video on a real SNES, announced a few days ago that he wants to create controller rumble support that will work on a real SNES!
http://forums.nesdev.com/viewtopic.php?f=12&t=19279
Just like MSU-1, a hacker would have to add rumble support on a per-game basis. The idea is to use a PC gamepad that already has a rumble feature. I would assume byuu would allow this to work in his emulator, but he also stated that his goal is to have it work on a real SNES console if you use a controller adapter. A controller like the Logitech F710 would be perfect.
I think this would be extremely fun to mess around with. Imagine F-Zero where the controller rumbles while you're taking damaging, and how hard it rumbles depends on how much damage you're taking. Or Super Mario Kart, it could rumble if you're off the track or when you get hit by an item. Or you know in a platformer when something stuns you? Like the big Hammer Bros in Super Mario Bros. 3. The controller could rumble at 100% the entire time you're stunned. Star Fox is a no-brainer.
Project Announced: SNES Controller Rumble Support!
Re: SNES Controller with Rumble Support!
FFVI
>gets to world of ruin
>controller explodes
>gets to world of ruin
>controller explodes