Your favorite FPS gun EVER.

Borderlands 2. Double Penetrating Unkempt Harold.

Nothing is more fun then shooting a barrage of explosions upon your enemies

Lots of the crazy weapons from Saints Row 3/4 - the Dubstep Gun, Shark gun, American multi-gun, etc.

Depends on the Borderlands 2 character I use, but...

Type 2 Fibber pistol for an "anarchy" Gaige. Butcher shotgun for everyone else.

The P90 is a thing of beauty, whatever games it might be in.

The Flak Cannon from Unreal Tournament for me.
Or the Drunk Missile from Rise of the Triad. (original or remake, both work)

For 3rd-person shooter, Mr. Toots from Red Faction Armageddon.

The BFG In quake guess .... Hardly played any fps since I despise the genre , but that was 1 fun gun to use

M1903 Springfield and MP44 also called StG44 (Sturmgewehr 44) from the same game/time.

While it wouldn't be my favorite since I've never even played the game, the most interesting gun that I'm aware of would be the Alien Arm Gun from an old game called Redneck Rampage. It was a dismembered alien arm that was still clutching its gun, and you'd fire it by yanking on the tendons that would pull the trigger. :P

View attached image.

Plasma Cutter and self made guns from Dead Space.

the bane from borderlands
0.34 min for info
https://youtu.be/HjK5NsjvnI4?t=34s

MTAR - Call of Duty Black Ops 2

That shotgun out of the Borderlands 2 Tiny Tina's Assault on Dragon Keep DLC that fires exploding swords at people. It really brought a smile to my cynical face.

Dragon's Breath shotgun from CoD Black Ops

View attached image.

The Rainbow farting Unicorn from Red Faction! :)

the cerebral bore is pretty damn great too

Buck's assault rifle, which is a shotgun at the same time, from Rainbow Six Siege.

Shotgun from Doom modified to use fist as ammo and all animation frames removed would be favorite for efficiency.
Rocket launcher from Doom modified with additional speed so the rockets go through walls in elliptic curves around the map and negative damage so when they hit something they implode healing everyone around for lulz. :)
And real Doom, not some silly remake kids today play.

Redeemer from UT. Also Flak Cannon from UT. I love UT. I'll play UT. I'll never stop playing UT.

The .223 pistol from FO2

Duke Nukem 3D's DEVASTATOR is super satisfying.

gravity gun (Half Life 2) & Portal Gun (Portal) ;P
the BFG in the last Doom wasn't bad either

Too many guns to choose from, most are less or more the same generics....I don't know, for now, the Colt 1911 from Mafia:City of Lost Heaven? It sounds amazing, it's deadly precise, it hits hard, satisfying to both shoot and reload, reloads relatively easy and fast, beautifull looking gun with a good looking grip, awesome gun, it's also a blast to blast at foes with the shotgun.

The Uzi from the GTA series has been a staple and I love it, but my most favourite gun from the would be the Kruger, which is exclusive to Vice City saddly, I like the Mac 10 too, GTA IV has the most satisfying gun useage as even the basic pistol is a pleasure to shoot, but in V it's all ruined and shitty. Enjoyed firing the AK47 3, shotgun was fun in San Andreas.

RPGs and rocket launchers are my favourite in any game, but oh boy do they really suck in Uncharted 4, small damage radius, not enough power to kill on direct hit I don't think, reloads slow and limitedly.

It's satisfying to blow away Specimens in Killing Floor with any shotgun or managing a headshot streak with pistols and the MBR14.

I love the Sentry Gun in TF2 when it mows down enemy players , it happens so rarely saddly, setting up is a pain and the nerf that minguns do more damage to them didn't help, the huntsman, shotguns and revolvers come in second.

Alot of weapons from Half Life 2, look good, sound good, shoot good, the revolver, SMG which doubles as a grenade launcher, self reloading hard hitting and sounding lmg, sweet stuff.

Maybe the Settler pistol from Rage was satisfying to land headshots with when loaded with the biggest bullets called fat boys or big momma's or something.

The flamethrower from Fallout 3 was lovely to burn foes with, the sniper rifle is also sweet to use , such a good design in everything, but the rocket launcher and grenades take the cake.

Dead Space has among the best "guns" to ever have been made, Pulse Rifle, Line Cutter, Flamethrower, Plasma Beam, Force Gun, Javelin Launcher and much more, sweet, sweet arsenal there.

The Black Butterfly and the Magnum 7 from Resident Evil 4 were absolutely satisfying to use, magnums, awesome guns, pistols were very nice too.

High caliber pistols and revolvers in State of Decay make some sweet shooting.

The nano Rifle from Red Faction Guerrilla is a real monster, true predators tool of murder, very cruel to living beings yet so effective. The shotguns are also awesome at blowing enemies away.

Call of Duty 2 or 3 specifically had those yellow bolt action rifles for the British that I absolutely loved and enjoyed using, favourite call of duty gun right there I think.

Killzone: Liberation had very satisfying shotguns and LMGs and Smgs, sniper rifles, turret guns, revolvers, rockets to the face, very good weapon selection there, very satisfying to use those.

Resistance: Retribution had fantastic weapons like the Auger which was satisfying to use as well, it also could shoot trough walls and the force fields it could employ to protect you, very good gun but even the standard assault rifle was delightfull to use.

The Smgs. In Saints Row the third were kinda sweet, loved the design but the exploding bullet pistols were bloody badass too, shotguns as well.

Counter Strike, Glock, Dual Berretas\Elites, Mac10, MP5, TMP, FAMAS, P90, COMMANDO, XMO pump action shotgun are my favourite guns in, probably incorrect but should be a rough good enough idea what I liked.

Defiance had some nice Smgs I think I remember.

It's lovely to shoot guns at enemies in Crimecraft, the guns from there are all very unique, not real but still great and they feel good to hear load at bastards, from pistols and shotguns, to assault rifles, rocket launchers and grenade launchers, awesome gameplay right there with wonderfull underrated gore to boot.

Arctic Combat and District 187 had some great implemented hard hitting good to use guns, can't expierience that anymore no though saddly...

Filling chaos marines with lead with satisfying sound to go with in Warhammer 40K Squad Command was swell.

Executions with guns from The Godfather 1 and 2 were absolutely satisfying, I do recommend looking up videos on it.

Revolvers in Borderlands 1 were satisfying.

Jurrasic Park Rampage Edition blessed my childhood with. Electricity gun that turned enemies to dust, same with the Flamethrower, it felt and looked beautifull and satisfying on a massive scale, bombarding enemies with grenades was lovely too, and it was sweet firing the SMG as well, so many bullets.

Let me tell you, it's satisfying to get a kill in I Am Alive, one way you get those is with the pistol.

The guns in Silent Hill Origins felt satisfying.

The assault rifle gun mounted wheelchair in Dead Rising 2, need I say more? Dead Rising 1 guns felt way better though, they definitely sounded Waaay better.

That's all I can remember, think of, that's hard to do...

AvP 2. The Predator weapons.

For pure '**** you' to all other players, it was the dual miniguns of TimeSplitters
https://youtu.be/MqqNPTKfzu4?t=3m46s