Zeidrich2004 said:
Hunting Rifle in Left 4 Dead.
I main Hunting Rifle. It chews Special Infected up something tragic. I get a lot of Smokers ragequitting in Vs. :3
It's great for hordes, too, since the bullets travel until they hit an object - a few bullets can empty a hallway. A lot of people don't see the utility of the Hunting Rifle until they're in a team with someone who has been using it a while, but it's pretty much essential to have at least one Hunting Rifle player in Expert Campaign or against an Infected Vs. team who knows what they're doing.
Anywho...
Death in any FF game, though Doom is quite delicious.
Flamethrower in the first Red Faction, and many other games. The Flamer in Fallout 3 is a BIG exception.
Sniper Rifles in Mass Effect.
LMGs in Rainbow Six: Vegas, unless you're playing Attack and Defend and you have your bag sitting in a hallway or something.
Boltok in Gears of War multiplayer. It's great for killing Wretches in the Single Player, though.
Overlord in XGRA. You'll never hit anything with it, and it doesn't instant-kill. Made worse by the fact that one more powerup item will get you the SINN Deathstrike, which never misses and will instantly wreck AI opponents.