I'm starting with Yukio for a couple reasons: 1. He is pretty level-headed(ignoring the whole "Satan took over his body" thing), and 2. He can help with keeping my next choice under control.
My first round pick is Rin, Yukio's older brother. I picked Rin because he has proven that he not only has some serious power, but that he does have(at least, some)control over it.
My second round pick has got to be Impulse. Mainly because he is a bad ass. He's proven to be a team player, and he is as fast as the Flash.
For the 3rd round I decided on Aang(particularly when he is in the avatar state), because he has ultimate control over the elements. Aang may be light-hearted and fun loving(maybe even a little goofy), but when it matters, he is someone who can be counted on.