the M4

what's the point of mentioning the M16 without mentioning it's square root the M4, it's a simple, low recoil, decent damage, quick reloading all round good gun, it is handy and is given to you as a starter in some of the earlier missions.

as mentioned with some of the earlier assault rifles this one benefits from careful planning, in campaign mode it benefits hugely from head shots quintupling it's damage, so aim at your enemy's head as much as often

one of the most common setups for the M4 you'll see in the campaign is sopmod, basically supressor, m203, and red dot. this gives you a very mobile and stealthy weapon, and yet again with a bit of alertness you have a very dangerous combination