the shotgun and grenade launcher aren't that good compared to the AK-47. Shot gun spreads too much (possibly more during jumps that are necessary to play) causing bullets to pass by enemies at long-medium distances. Grenade launcher's range is too limited, causing it to have effect in the "danger" zone where enemies will shoot at you where your distracted by the angles you have to calculate, air borne that don't have a hard time dodging, and the constant stream of grenades and explosions.