Ask The Wasteland ponies [Hybrid]

Hybrid weapons aren't bad if they are the right combination. Militaries use grenade launcher attachments with assault rifles, and even shotgun attachment are available. But weight is indeed an issue, not to mention that you have twice the ammo to carry.

A hybrid energy weapon would work. Laser for mid to long range and plasma for CQC. But that's double the weight, so you wouldn't be able to carry many extra weapons. But the versatility in one gun would count for something.