No one can tell you which is the best gun for you, it all depends on how you play. You like close quarters then go for MP7, UMP or shotgun, want just an AR then go for M4A1 or M416, like sniping then either L9 or a semi auto. People can give you their opinions on guns like what's the most accurate and what has the least recoil etc but the best gun for you can only be answered by you.