Mass Effect 2 isn't lacking in big guns and satisfying explosions. Still, if you're already tired of the existing arsenal, consider checking out the new 'Firepower Pack' add-on.
For 160 Microsoft/BioWare Points (that's $2.00), the DLC adds three new weapons to Commander Shep's locker. The first is a 'hand cannon' type weapon, called the Phalanx. It hits hard and comes equipped with a laser sight, for the less-than-accurate gamer.
The Mattock heavy rifle is described as a sniper rifle "without the scope" and an assault rifle "without the recoil." Think of it as a hybrid weapon, one that can be used by any class.
The third gun is the Geth Plasma Shotgun. It looks similar to the Geth Assault Rifle, boasts three barrels, and offers better range than other shotguns Charge it up for a high-powered blast.