For me it would be the fact that I'm roughly equally skilled with all the primary weapon groups, I'm not claiming to be a great player or anything but I can pick up any weapon off the ground, know how to use it and then do ok with it. I might not be the best player but I am versatile.
The only things I really cannot use in this game are Tactical Insersions and pistols, never got the hang of either of those.
