The upgraded flamethrower from Jazz Jackrabbit 2, I burned through the whole game with that.

Gotta be the Portal gun. I want one in real life.

Gravity Gun is nice though.

Aperature Portal Gun (Portals)
Wrist Blade (Assasins Creed)
Buster Sword (Final Fantasy 7)
Calypso (Perfect Dark)
Bee Swarm Plasmid (Bioshock)
The Redeemer (Unreal)
The AWP (If you don't know you should not be here)
Needler(Halo 3)
Kain Drain (Legacy of Kain: Defiance)
Blue Shell (Mario Cart)
M16 (Call of Duty 4)

Silent Hill ( the Original) - Fireman's Axe, you could beat every enemy but the last boss with that thing.

Hidden Blade (Assassin's Creed), because they never see it coming.
Deathtraps (Goldeneye: Rogue Agent), because often there is a moment of realisation on the part of the victim.
Sniper Rifle (Halo 3), because you have to love the *Boom! Headshot* factor of it.
And, of course, the BFG9000 (Doom. Duh). A great big middle finger to aim and/or accuracy.

propertyofcobra:

3: M1 Garand.
This rifle is just...lovely. It's powerful and accurate. My weapon of choice in any given WWII game.
And of course, the noise it makes is wonderful, absolutely sublime. I shouldn't have to say much about it, really.

Oh god. I'll go reinstall Medal of Honor AA now.

Hammer of Dawn(Gears of War)
The exploding Sheep Gun, idk the name(Ratchet: Deadlocked)
Supernova, when it's level 10 and it has the Jackpot mod, and full ammo mods, not only can you PWN everyone in sight, you gain like 1000 bolts per person(Ratchet: Deadlocked)
Gravity Hammer(Halo 3)

and last but not least...THE BFG!(Doom)

(1)Blades of Choas (God of War)
(2)Lancer Assult Rifle(Gears of War)
(3)the Gravuty Gun (Half-Life Two)
(4)Portal Gun(portal)

wow... why has nobody said anything about the P.R.L. 412 for resident evil 4!?!?
its a fuckin doom gun
you don't even need to aim the fucker, just charge it up and point in your targets general direction then fire and anything that can be broken/killed will be broken/killed!
p.s. you get it from finishing the game on pro difficulty

Devil May Cry 4

Pandora's Box - This thing is godly. Not only does it change into 7 different things, but once you fill it's bar full it can instantly kill everything on the screen.

Lucifer - a Vergil wannabe but who cares cause it's cool, and you can throw a rose to finish them off.

TJ rock 101:
wow... why has nobody said anything about the P.R.L. 412 for resident evil 4!?!?
its a fuckin doom gun
you don't even need to aim the fucker, just charge it up and point in your targets general direction then fire and anything that can be broken/killed will be broken/killed!
p.s. you get it from finishing the game on pro difficulty

Never cared Enoughf (spelled that wrong I know)to get it so didn't put it on the list

Most of the guns from the original UT were awesome. Flak Cannon, The Ripper, Redeemer, Instagib Gun...

Apart from them, though the Worms Super Sheep and the Gears Chainsaw are my top favs at the moment.

a gun that freaking shoots shuriken and lightning, painkiller, and no i did not rip of from Zero Punctuation, really surprised he actually reviewed that game, but that thing is freaking awesome, plus a gun that shoots trees, damn.

Ahh... hm...
Well, here are some. I'm sure I'll think of some later, but for now, I think I'll settle for these.

Sol Blade-Golden Sun: The Lost Age
Moo 2000-South Park 64
"Shuriken and Lightning" gun-Painkiller
Painkiller-Painkiller
Gravity Gun-Half Life 2
Hyper Mode Beam-Metroid Prime1/3
Annihilator beam-Metroid Prime 2
Spartan Laser-Halo
Gravity Hammer-Halo
Aperture Science Handheld Portal Device-Portal
PowerCannon-Megaman Battle Network 1
Spiked Flying Blue Shell-Mario Kart
Exploding RC Cars-GTA Vice City

It would have to be the Bullgut from Shogo:MAD
Granted, its just an update of the drunk missile from Rise of the Triad, but it was just so much fun to shoot. Shogo had such wonderful explosions that you would be certifiably insane not to enjoy shooting this gun.

Another favorite was the SADAR from Aliens vs. Predator. Never before had a rocket launcher been a marksman's weapon, and no plain rocket launcher has been anywhere near as much fun to use since. Use a smartgun to help you spot one of those sneaky predators, switch to the SADAR, peg him in the face with an anti-armor rocket from 20 meters and watch as the wave of fire and smoke rolled past you and back down the corridor.

And for a little variety, the Quake 2 BFG was my favorite. Also, BFG really stands for Billion Fireball Gun. In its original incarnation it spit dozens of plasma rifle shots but was changed to the big green ball we all know and love shortly before the game was finished.

What was that sniper rifle in perfect dark called again? It had an X-Ray scope and shot through walls.

Wakka Wakka!

cmon, just imagine having license to launch the spiky one at somebody/something flush in the face :D

Ah yes, FarSight, the only weapon banned in casual play between me and my friends. We all agree on it.

That being said, my favorite gun, by a very large margin, was the Dragon. Every time I killed someone, I'd throw my Dragon right on top of that stack of guns, then just leave.

For those of you who haven't played Perfect Dark, throwing your Dragon turns it into a disguised proximity mine.

Mr. Domino

I also like the God of War insta-kill grab attack, or as Yahtzee put it, the 'F*** you button'.

Every game needs a f*** you button.

The Lancer Assault Rifle from Gears of War. It's an automatic weapon with a chainsaw attached to it. Hard to get much more awesome than that.
Also the Torque Bow. One of the most satisfying kills I have ever experienced, involve Boomers and Torque Bows. It's funny how many times they'll say "BOOM" right before they explode.
I'm kinda surprised no one's mentioned the Redeemer from Unreal Tournament. Portable, guidable, thermonuclear weapon.

the gun from painkiller that shoots shurikins and lighing
the only way it could be better is if it had tits and were on fire. hahaha lol
either that or sam fisher's hands and knife. he's like a ninja with an assault rifle. =)

the PainKiller (painkiller)
The chaingun/rocket launcher (painkiller)
Genocide gun (Earth Defense Force 2017)
BFG9000 like so many others
portal gun (portal)
gravity gun (half-life)
remote bombs (Bomberman series)

I have to put this here before I give my favourite weapons:

I'm not a psycho, I hate real life violence. But in games I will do anything I can to torture NPC's and ragdolls.(this is one reason why I don't play Gmod when other people able to see me playing)

Stake gun - Painkiller
Gamorrean Cleaver - Star Wars KotOR2(huge axe used in one hand, it's about half the size of your character, in the game you can't really torture but it's more the idea of using a huge axe to repeatedly hack in an NPC until it dies)
Crossbow - Half Life 2
Harpoon - Half Life 2 Lost Coast(like the stake gun and crossbow I love to use it to pin enemies to walls)
Chainsaw - Serious Sam: the second encounter(if this is the Gamecube version)

The monkey gun from timesplitters 3.

Pull the trigger, and the ENTIRE clip (64 bullets) fires in about 2 seconds.

Oh yeah, I can't forget the bricks either.

no particular order

remington 1100 in GTA4
the Ban Hammer in Halo 3
lancer in gears of war
the AK101 in BF2, that shit RAPED.
the M40 in Opposing Force gave me a woody.
Clan ER PPCs in the Mechwarrior games. Fuck you Inner Sphere stravag scum.

fags.

sniper rifle(sniper elite-bullet time)/Key(kingdom Hearts)/Lightsabers
Gravity Gun/Bioshock's plasmids
Rocket/Grenade Launchers(and things like BFG9000 doom)/redeemer Unreal Tournament
halo swords/sticky's
Gears of War(that chainsaw weapon)

The Redeemer (the UT games)
Plasma Grenade (Halo games)
Chainsaw gun (Gears of War)
Zero-Point Energy Field Manipulator (Half- Life 2)
Aperture Science Handheld Portal Device (Portal)
Infinite Rocket Launcher (Resident Evil 4)
Reaper (Perfect Dark)

the Pistol in Bioshock because it looks goofy and you find it in a baby stroller, or the shower head from dead rising.

RPC 90 (goldeneye)
M1 Garand (any WW2 FPS)
warthog (Halo)

The Chemical Thrower from Command and Conquer: Renegade. It's like a flamethrower, but it poisons the ground and can turn enemies into Tiberium mutants when they die.

Heck, EVERY gun in that game was awesome. The sniper could zoom to about 100000 miles.

The spy corvettes from homeworld cataclysm. I cant remember what exactly it was called, but there was just something so satisfying about disguising one of those flying bombs as a enemy frigate, and then detonating it right next to a enemy heavy cruiser. and you could link a pair together to make it that much more powerful.
the morphoray from Ratchet and Clank
the Rynicerator from Ratchet and Clank, Up your Arsenal
Spartan Laser from Halo 3
spike grenades from Halo 3
Ultima Keyblade from Kingdom Hearts(the only one that actually looked like a sword, I love those games, but god they had a crappy main weapon.)

BuckminsterF:
the shower head from dead rising.

Probably the most brilliant idea in any zombie game I've seen.

Whatever is at hand. I would go plowing through some teorrists with my bare hands if I had to.