My friend Rob sent me this suggestion in an email...
To balance things out for superhumans (or Anyone else) have you considered using “What’s your Kryptonite?” The players pick something in advance, roll on a table, etc for something (or someone) that will nullify, limit, remove, knock them out, etc. the use of their power. For that matter, each use of the powers could build up in a pool of dice or something until a threshold is met that causes an unexpected side effect (perhaps a good way to go with mutants), or an inability to control their powers or something malfunctions. Lots of roll play options here.
I figure there are already mechanics in place for both limitations (things that tamp down or set frameworks around your powers) and drawbacks (generalized problems you have such as a phobia, secret, allergy, or susceptibility to an attack form). I think I have things in place, or that will be in place, to address most of these ideas. Stunts are things that push your powers beyond their normal limits, but which come with a potential cost.
However, I liked the idea of some chaotic sort of thing... I don't think it's a gift (necessarily) ... it could be a talent. Or a drawback. Not sure yet. Here's the pitch:
When you roll a resolve die, there is a chance the die is wild; a natural maximum result (6 on D6, 8 on D8, etc.) is a wild die; keep the result, but roll again and keep adding results as long as you keep rolling the top result. However, if you roll a natural 1 on your first die of any resolve attempt, something chaotic and bad and messy happens... you suffer damage, or your powers stop working, or you knock yourself unconscious...
This mechanically almost feels like Joker/Harley insanity; they have points that they can throw into things that can work out great or terrible for them. I'm almost thinking that this works better as a villain ability. I like the idea of having a set of villain-specific gifts that help to emulate villain types. I mean I could just call it 'controlled chaos' or something like that. It could be as simple as once per round, you get to add 1d6 to any one action, resist, or result roll. If you roll 6, the die explodes and you get to roll again. However, if you roll 1, the action goes horribly wrong.
It definitely feels like this belongs in the villain list. I like the idea that there are a significant number of mechanical options for villains so that a battle with Riddler feels different from a battle with Joker, or Mr. Freeze, or Catwoman... you get the idea.
Something to continue to mull over.