I'd have to say, either between the MP5, M16a4, or M4. MP5 is great for close quarters combat, decent at medium range. The M16a4 is good for a medium-long range assault rifle, or marksmen rifle, when the Acog is attached. And, the M4 is fairly good in CQ, close quarters, and medium range. But, for my play style, which is sneaking to a flank and getting the enemy at their side, I like to get close. So, for this, I'd have to say the MP5 attached with either a red dot, or suppressor.