If i could have one superpower, it would definately be super speed, just imagine all the cool stuffs you can do with it.

Lets start with the mundane things, you wake up late, you start the car, got stuck in traffic, and bam late for work, not with super speed, you cand just waltz there in a jiffy. Now you're at work, you forgot that your boss gave you a pile of paperwork last week and the deadline is today, super speed? Hell yes. Well thats just a small sample of everyday things being easier due to super speed, want to kick it up a notch?

Remember physics 101, e=mc2, superman better take a back seat, you'll be throwing the hardest punches for a long long time. Time travel is also in the realm of possibility due to relativity, as long as you go fast enough, imagine all the fun uses of that eh, time at your disposal. Well actually everything is connected to speed so yeah you'll basically be all powerful and all that.

The downsides? Hmm i dont know, probably none? Well besides getting drunk with power and starting a dictatorship. You could actually also mess up the time line a-la flash in flashpoint crisis. It would probably also make a lot of physics and biology theory irrelevant or incorrect, that'd be a big problem for educators surely, they'd have to relearn what they teach haha! Oh wait, friction would probably be your only weakness, but i'd imagine someone will discover a material with superlubricity sooner or later, frictionless air bubbles and super teflon anyone?