There is a new bug that allows players to apply the traits of special REQ weapons onto other weapons, which can result in some rather ridiculous combinations.
If you plan to go into Forge and try this out for yourself, here are some combinations I would recommend:[spoiler]Rocket/Ad Victoriam > Spartan Laser (aka God Killer) (aim down sights)
Carbine/Rain of Oblivion > Shotgun
Plasma Launcher/Scourge of Fire > SAW
Plasma Launcher/Scourge of Fire > Scattershot (aim down sights)
SMG/Projection Sight > DMR
Boltshot/Closed Fist > Halo CE Pistol[/spoiler]