1 - Noob tube / Thumper
I don't mind getting tubed if I'm tubing (to annoy whiny kids), or if I'm camping (I probably deserve to get the **** tubed out of me). But if I'm playing normally and I get tubed it's annoying because it's easy mode. You could shoot me; but no, out comes the grenade launcher with the power and fatal blast radius of a mini nuke. That's why it's nooby.
2 - Akimbo Rafficas / Models
Gah I hate these. Point anywhere in a 60 degree arc around where the enemy is, click both triggers and get your easy kill.
3 - ACR
What's recoil? This is laser beam accurate and quite powerful to boot.
4 - MLC TacKnife
Not a gun, but deserves a place on the list. People that run around like Usain Bolt on speed knifing - it's the fact they can lunge from 10 metres plus to get you while lag protects them from harm. Not so bad on open maps like Derail (because they usually get sniped repeatedly, give up and try something else), but get one or more on Favela or Skidrow and FFUUUUUUUUUUU it's rage quit time. You shouldn't be able to bring a knife to a gun fight and win consistently.
5 - Akimbo G18s
Far more accurate than they should be.
6 - UMP-45
3 shot kill at any range = OP. Silencer has no negative effects at all!
7 - PP2000
Same damage as the UMP up close - and this is a SECONDARY (Stopping Power = 2 shot kill). It's quite accurate too. I've gone 26-7 using ONLY this on TDM. Add extended mags and you have a gun that's better than most SMGs. Definitely OP
8 - Any sniper except the Intervention...
...because they can be spammed. At least the Intervention needs to cycle the bolt between shots so you can't spray. The Barrett is worst for this - not only is it the most powerful but with a good trigger finger it fires faster than most automatic weapons!
9 - AA12
Automatic shotgun... really? At least the range is ****. Slap on Extended Mags and give it to a sprayer and it's noob central.
10 - RPD with Grip
Almost ACR levels of accuracy... with a 100 round mag. A spray and prayer's dream. Fire rate and reload* are slow, at least.
*Update: it's a 2 shot kill at any range with Stopping Power, and OMA Pro changes the 10 second reload to 3 seconds. For an automatic that's OP.
I can (and do) live with this - it's just a rant. I also know there are loads of similar threads out there but wanted to get my two penneth in. My experiences come from using and being killed by the above.