I also vote for the Juruense, though it may not meet your 'eat everything' requirement. Problem with getting RTCs and TSNs is that you basically have to give them up for free to the petshop once the either one of them gets beyond 16 inches, and you have to have good relations with the petshop as well in order to do it most times..
Consider these 'not so monsters' but interesting cats nonetheless...
Chaca sp.
Pseudopimelodus raninus
Jaguar Catfish - Liosomadoras oncinus
For more of an 'odd-ball' cat, try some from the Cetopsis genus. Having a small school of around 4 individuals should be pretty neat. Small versions of the Paroon shark, IMO. I haven't kept them, but I have read that you can't mix them with any fish, as they will attack everthing in the tank, regardless of size. I have absolutely no idea if this is totally fictitious or not, but if anyone has kept them, I would be interested if this was true or not. They sure are pretty neat looking though!!