What is the best super power?
"In a world where few or none have superpowers, the power to control people (I don't care about actually reading their mind, I'd rather control it)."
Ah but isn't it already possible to control most people with money? :P
"In a world where many or all possess superpowers the power to turn off superpowers in people at will is the best superpower."
Makes sense, you could have an army of superheroes depending on you to let you use their powers. You could potentially unify all super heroes under your (hopefully moral!) control.
Personally I'd love telekinesis, but then the ability to do like Naruto does and create "clones" of himself that all go out and learn then when they snap back to him he gathers their knowledge all in one fell swoop is pretty cool. It'd be nice to have a clone of me go to work, I could hold about 4 jobs and relax while they do the work ;D
Power absorption into regeneration. Basically as you get hit you absorb the energy and then use it to regenerate yourself to get stronger. So no matter how powerful your enemy is if they keep hitting you then you eventually will overcome it and them.
Generally I find invincible super powers to be boring and cop outs. What makes this one different is the holder actually has to suffer some to accumulate the strength to overcome. Which although a tad masochistic also lends a sense of heroicism to their eventual victory. The holder could be a basic average person in daily life and only actually achieve this higher state after extreme duress. In other works it makes average Joe the eventual ultimate hero.
In comparison, Superman is utterly boring until someone introduces kryptonite and finally makes the contest interesting. Superman is almost the opposite of what I describe - staring out utterly invincible and then having just that one little sliver of possibility he'll be brought down to size.