I have been so busy but I finally have time to address the Homework question that @missy and @rambo asked for Comic Con.
If I could have any super power I would want to have the power of intangibility: the ability to pass through solid matter. I can think of no greater ability than to be able to get out of any tight spot. There have been many times in my life when I have felt trapped, not necessarily physically trapped but emotionally. When I think back to those times I almost feel claustrophobic in my own skin. The idea of being able to escape anything is very attractive to me.
Now let's also consider the practical and possible evil implications of an ability like intangibility: In a Super Hero battle you could really run out your enemy's energy by phasing through walls and making them come after you, all the while attacking them from other angles using the element of surprise (assuming they don't have x-ray vision). As a villain with this power it would be all too easy to become a master thief and very difficult to keep you imprisoned if you do get caught. Although you would not be able to travel as effectively as you could with the power of flight you could travel covertly and maybe even using under ground passages whenever possible.
Also practical jokes would be super easy.
I am sure there are so many other great ways to use this ability that I cant even think of.