This question comes up a lot with my friends, and I gotta go with Green Lantern. Not just because green is my favorite color, not just because I'm a fan of Hal Jordan, but because his power can essentially replace most of the powers up there. He could fly in a bubble, create his own claws, replicate the effects of super strength through tools of his will, etc.
A close second would be Quicksilver, who's similar to The Flash, but while the Flash is fast down to a molecular level (can actually walk through walls by vibrating his molecules around others), Quicksilver is also mentally fast, and can learn things at super speed (If I remember correctly he once pounded at piano and within minutes was playing classical music).
Cat's out of the bag: I'm a huge nerd.