RPG

 is a gun that fires explosive rocket-propelled grenades that accelerate over a short distance.

Trivia

 * "Leveled Up" references a common game mechanic in role-playing games.
 * The synergy is a reference to Final Fantasy VII. The hero Barett mutters this in disparagement of the Midgar arcology (a city contained within a single bullding).
 * The player can shoot through locked doors with the RPG by standing right next to them, and can use the explosion to knockback items back through the door.