Favourate lethal weapon is the m4 carbine from CoD 4, with silencer.
Favourate non lethal weapon has to be the portal gun hands down.

The Railgun from Red Faction. If you don't remember what it is, the Railgun was a instant kill weapon that shot a depleted uranium metal slug through any material (i.e. concrete, metal, rock, flesh and bone, etc).

Instant kill weapon + infrared scope + firing through walls = epic win.

Where to start?!?

Sci-fi: Railgun, BFG 10/9K, the nano-suit (Crysis) and Ion Painter (UT 2004)

Modern: AK-47 with G30 under-barrel grenade launcher, Desert Eagle .50 cal, smoke grenades, Dragunov, Barret .50 Cal and the XM8 (AKA the SCAR from Crysis).

Fantasy/past: ninja-style swords and shurikens.

AK-47 in CoD4

Or the Tak gun from Crysis

Farsight XR-20, from Perfect Dark, a rail gun that could shoot through anything, equipped with a scope that could not only see through walls but also home in on targets. You can run, but you sure as hell can't hide.

I haven't even used it yet, but I'm gonna have to say the Splicer from Resistance 2. It's about as close to a chainsaw launcher as you're gonna get, and damn does it look satisfying to use.

Edit: And the second shotgun from Cod4. I love that thing, just the sound it mkaes on contact... thump.

Timesplitters(all 3 games): Brick. 1 hit kill at close range!! And bounces off walls!!
Paper Mario: Coconut. "Throw it to damage 1 enemy."
Pikmin 2: Purple Pikmin. Throw them onto anyone and anything to slam them senseless for a few seconds.
Whiplash: Electro Bunny. Chain shocks anyone near you!!
Perfect Dark: Farsight. Brings sniping to a whole new level...
Any Game: Flamethrower. Medium or well done?
Any Game: Plasma Gernades. Hahahahahahahahaha suckaaaa
Worms 3D: Dynamite. Plant it, 5 seconds to run faaaar away.
Any Game: Unarmed. EAT MY FISTS!
Kirby 64: Dynamite, Laser Sword, Flame Sword, and Shuriken. Kaboom! Darth Maul! You can throw it! Stick them and boom!
And greatest weapons ever... Unreal Tournament (All 3 games) THE REDEEMER. IT'S A NUKE.
Starcraft 1 and 2: Nuclear Strike. Boom.

haha deffo the gravity gun

Other than that i'd have to go with the Lancer from Gears of War, the chainsaw beyonet is great fun

I also really liked Squalls GunBlade in Final Fantasy 8,

1:the healing gun from tf2.keeps your team yelling "medic!"all day long.
2:the baseball bat
3:the crowbar

The worlds most interesting bomb.... MDK!

Portal gun especially if it can be added to CS:S
and the physics gun same as above.
and yah the official name for the grav gun is the physics gun.

Hmm, I go with the Gravity Cannon from Sylpheed, I mean a black hole firing gun that straps to the bottom of a supersonic space fighter jet, its instant high speed vaporisation. Whats not to love?

Merc 2 nuke, not my favorite game but bout time we got a REAL FPS nuke

the Scout's Baseball Bat in TF2. Running around like a maniac beating a guy down over the process of a couple minutes is really gratifying.

TheBadass:

Edit: And the second shotgun from Cod4. I love that thing, just the sound it mkaes on contact... thump.

no,no,no

BudZer:

On topic: The RYNO from Ratchet and Clank, while it doesn't look very spectacular, it works wonders.

very much agreed.
Also, the the Blue Grav. Gun from HL2 (bet you're all thinking of that anyway).

Monkeyman8:
the official name for the grav gun is the physics gun.

I believe it's the Zero-Point Energy Field Manipulator

ElephantGuts:
Fuel-Air RPG. Mercenaries 2. Orgasmic.

Second that, along with pretty much every airstrike. Beautiful destruction, even though they are completely pointless.