I'm glad more people don't use the M16 w/ ACOG scope, because that combination is lethal.

Proximity mines, Goldeneye.

I love the Hammer of Dawn from Gears of War. It's a very limited weapon, but I use it whenever I'm able.

I'm also partial to the MTAR-21/TAR-21 from the Rainbow Six: Vegas games.

COD 4-P90 and Barret(spelling) Sniper
Killzone 2-Lighting gun but can only get it in campagin
Resistance 2-Marksman, Magum and Wraith

The Shotgun in most games. Blasting it in close rage always put a smile on my face

Marathon Series: MA-75 assault rifle. It's your typical assualt rifle + grenade launcher design, but it has a nice big magazine full of grenades. Which is good, because blowing yourself up with a grenade is the only effective way to jump in this game. Blowing myself up never felt so productive.

Unreal Tournament: Flak gun. Devastating at short or medium range with a fast firing rate. Close second is the biosludge rifle. Despite being short range and damn hard to use, a fully charged shot does so much damage that it's totally worth it.

Battlefield 1942: M1 Garand. The accuracy of a long barrel rifle makes this weapon a threat at any range. Throw in semi-auto action for a series of fast and accurate follow-ups if the first bullet doesn't hit brain and you won't find a more dangerous infantry weapon in this game.

Half-Life 2: The gravity gun. Do I really need to explain how awesome it is to crush your enemy's head with a radiator from twenty feet away? Or crush your enemy with another enemy?

Team Fortress 2: The flamethrower. There's nothing quite like flanking an enemy offensive, lighting a half-dozen people on fire, and watching their push fall apart as they scramble to find a way to put out the flames. Even if nobody dies, I consider it a pyrrhic victory to sow that much chaos amongst my enemies.

The Conduit: The shrieker. A semi-automatic weapon which fires laser-guided missiles. Hmmmm... Okay! Second place goes to the warp pistol's crazy ricochet. Watch out for the death blossom that bursts from those charged shots.

Halo 3: SMG= what me and my Halo buddy call the anti-noob weapons. Take down the noobs with shotgun, rockets, BR, etc. You name. Learn its power and it is the ultimate weapon haha.