It's all a matter of opinion, but here's what I usually run:
AN-94 with stock and fast mags Ghost/Blind Eye Scavenger Engineer Frag EMP
This is pretty much what I run for all assault rifle classes. Fast mags is arguably a waste of a point since the reload cancel time is almost as quick, but I would rather not have to worry about missing the timing. You can swap out Blind Eye for Flak Jacket. I happen to run into quite a few Hunter Killer users and I'd rather not worry about being targeted than having to hide.