Yeah, I've got a MIDI controller for it:
The M-Audio Axiom 25
It's a great lil' MIDI controller that does the job for me (it's what I used to do all the music on Trick-Or-Treat Adventure Quest
). I have messed with assigning the knobs to stuff like you're describing, but honestly, I mainly do most of my controlling/alteratons in Ableton Live itself. I hardly even use those handly knobs for anything. Only buttons I really even need to use on the Axiom other than the keyboard and drum pads are the pitch buttons. But I guess that really just comes down to what kind o' music you're doin.
I also have a Korg Triton Pro-X that I'd LOVE to hook up with Ableton, but don't have the desktop space for it at the moment because of all the other shit on my desk (which is why I bought the space-saving Axiom), so that bad boy remains tucked away in the closet. One day I'll take my old Triton friend out again, and ohhhhhh the sounds we will make.