In my opinion, these are the best weapons in each of the category (e.g. Assault, SMG etc)

1. Assault: M4, M14, G36c or AK-47
2. SMG: MP5, MINI-UZI OR P90
3. LMG: RPD OR SAW
4. SHOTGUN: EITHER
5. SNIPER: DRAGUNOV OR BARRET .50cal

Thanks, give these weapons a try and see what you think, remember, this is only my opinion. Add me PSN: MikeyJoe1404 (no spaces) and let me know what you think. :)