Let me start off with this: I have an extreme bias against Black Ops. Everything Infinity Ward did correctly, Treyarch attempted to "fix", and dulled down the multiplayer in doing so. Treyarch didn't seem to pay any attention to what players praised Modern Warfare for, and really only focused on complaints from what I can see.
Now, for the actual topic. Weapons that are under-used but perform very well.
-Recommended Setup: Extended Mags , Scavenger, Steady Aim, Ninja
The Kiparis isn't widely used from my experience, but what a lot of people don't realize is how much firepower this thing contains. With a rapid fire-rate and impecable accuracy for a SMG, it comes in handy in almost every situation excluding long-distance fire-fights. The recommended class setup provides you with generous ammunition, so your accuracy doesn't have to be perfect, excellent close-quarters combat and the possibility of stealthy flanking.
-Recommended Setup: Supressor, Extended Mags, Hardline, Warlord, Marathon
This weapon is more frequently used than the Kiparis, but is nowhere near as abundant as the FAMAS. Sporting hefty fire-power that's qual to the FAMAS and excellent accuracy at close-range, this setup allows for quick-kills in a stealthy fasion, while you rack up killstreaks left and right. The "Seinfeld" as I call it doesn't preform well at long range, however, burst firing makes up for it completely. If that isn't your style, extended mags will help you out a deal.
- FN FAL
-Recommended Setup: Masterkey/Flamethrower/M203, Lightweight, Hardened, Ninja
In ths set up, the FN FAL, a rare sight on the battlefield, can become your very own WMD with practice. Suppressing the thing won't really help it much, and it sounds cool without it anyway. Not to mention it has an intimidating sound.upon firing. With a generous clip, and the iron sights fine on their own, an underbarrel weapon can finally included in your loadout. Lghtweight and Ninja combined can be intimidating as well, as your rush ar your enemies head-on, popping 2 shots for a quick kill. In less than a second with great accuracy, the enemy can be down and you can continue searching. And for the long-range battles, hardened assists with taking out enemies behind cover.
- China Lake
-Recommended Setup: Scavenger, Sleight Of Hand, Any
More abundant than other weapons, but still uncommon on the battlefield, the Chinal Lake has the explosive radius of a moist peanut, but with a trained player at the controls, it can reign hell on the opposing team. Scavenger allows for extra grenades while sleight of hand eliminates the lengthly reload time on this beast.
- CZ75 (Dual Wield)
-Recommended Setup: Scavenger, Steady Aim, Hacker
Pistols don't tend to be used very often during firefights, and are the un-sung heroes of close-range combat at times. By pulling both triggers at the same time while Steady Aim is in effect, the player can kill enemies relatively easy and without much resistance. Scavenger assists in keeping up your ammo reserves while Hacker helps those who rush-head on to storm rooms watch out for claymores.