Overall most stuff is garbage. If we ignore old stuff you keep for sentimental value and Exotics (which are always available via Kiosk anyways),
Pulse Rifles: a vendor roll Hawksaw or equivalent roll PDX-45 from the Gunsmith. That's all you need. If you have a good Grasp of Malok, neat. Any others you have are probably worse and not worth keeping.
Hand Cannons: Finnala's Peril, Lord High Fixer, Eyasluna and The Devil You Know (maybe). These are close in base stats. Any you get with range boosts (Rangefinder, Rifled Barrel or Smallbore) are good. The rest of the hand cannons are probably not worth keeping. Revelator is technically capable of top-tier TRK but it's very unforgiving with that recoil and you need 2 crits 1 body because of the lower impact.
Scout Rifles: these things are very similar to each other. Hung Jury with the pre-April roll (or its black brother Tuonela) was basically perfect for PvE. For PvP, some Gunsmith Suros models are great, and if you're a good shot then maybe the original roll Coytus.
Auto Rifles: Doctrine with Counterbalance. Everything else sucks.
Snipers: You have the coveted 1KYS/LDR/Longbow family any good rolls with these (basically you want Shortgaze as a scope - bonus range or scope speed perks is great but not needed). Some lower impact stuff is nice for toying around like the KF sniper or a Trials/IB sniper. But yeah most everything else can go.
Fusion Rifles: FWC vendor roll is perfect. And it's still bad. No reason to keep all the split shifters and stuff you may have around.
Shotguns: quest Conspiracy Theory-D is great. If you find a party Crasher with Aggressive Ballistics and R. Barrel Then that's better. Anything else is unlikely to be worth keeping. Unless you want a quicker firing one for PvE - a Patch-A from Dead Orbit maybe? Most shotguns are garbage.
Machine Guns: KF one, Zombie Apocalype, Baron's Ambition, Bretomart's Stand, The Swarm. Take your pick. Anything that isn't lowest impact will work roughly the same.
Rocket Launchers: Ash Factory with Tripod and Grenades & Horseshoes or a Gunsmith Suros one with the same perks. Really no reason to own any others.
Sidearms: these are all the same thing.
Basically there's one or maybe 2 good archetypes per weapon type and 1-2 good guns in that archetype and then there's usually a single or maybe 2 sets of perks you want. Everything else is garbage.