This made me lol.
As everyone else has said
Kennedy
Stann
CroCop,
Thiago
Couture
Those are all top then after that the guys who I could see being real killers and a good shot, guys like Lesnar. I know he isnt popular around here but the SOB doesn't seem to like anyone and is an avid hunter who is a pretty good shot, not a sniper but not bad and as I said, I dont think would hesitate to pull the trigger.
Also someone said Chael, I like that answer because the guy seems pretty much fearless and is loyal to a fault so I am sure he would follow orders without question. The only question is how fearless is he when its his life on the line and not just his reputation.