Ark you just make me lol.
As for the characters :
Basically what you're going to want to look for is speed. Your want as much as you can get, but there IS a speed maximum of 2.1 as SFWC.
Main characters are Force Recon, Delta Force, KSF, ROKMC, and basically anything that's a male character. The rest is personal preference.
Some good items to optimize your speed are :