Farsight and Golden Magnum (DSRXL or something)- Already noted of Farsight's 1hit kill, that goes for this Magnum. A full shield 1 bullet, dead on next, both exceed as the games most powerful.
Photon Cannon- Charge up that sucker and its lights out for people! Though it works the same as Doom's Plasma Gun minus the auto-fire function, it is a versatile weapon.
Shrink/Expander Ray- Whats a better death to hear the enemies go splat under your boot or hear their organs expand too quickly and explode?
SSG- Takes over as main power house 90% of the time if no rockets/cells are available, makes quick work of big guys like Barons, Archies and Mancubi.
Plasma Rifle/Gun- pewpepewpewpewpew.... And.. well, it's quick, it's strong, though ammo is quite low a lot of time except in Slaughter styles. :I
Unmaker/Laser Rifle- One of the most over powered weapons in the series not counting the BFG. When combined with the 3 Demon keys, it shoots exceedingly fast, has huge power, and stuns a Cybie and even the Mother Demon. But it's fine because it's a bitch to get the keys, Omega has that little trick with the Red Key to enter the demon key room. The Lair has the shoot switch be-quick to jump kinda puzzle, easy though. The void is by far tricky, dont exit the level but step past the barrier and head to Blue key room, hit switch and run to the other side of level, timed of course.
Future Cop LAPD (PC/PSX)- Mortars Mortars AND A FREAKING Concussion BEAM! The Mortar (basic) is exactly how it sounds, shoot up and land-boom, but when you get the Advanced mortars... All hell breaks loose as you rain hell on the battlefield!-It shoots one huge mortar that splits into 7 smaller ones in a small circle, land all and an opponent is sure as hell dead! The concussion beam is strong with smaller ammo then most secondaries, but it does its job, but when upgraded it's a GTFO situation as it pierces through all targets aaand does heavy damage! When paired with the Mortars you have long and medium range hell on everything.