This may suprise a lot of you: Fully-modded Laser Rifle is my answer.

Most threatening things in the game are Cazadors or other pack-like creatures that move quickly, or Deathclaws, which are basically big-hitters. The fully-modded laser rifle has it all: the firing speed, the scope for precision, the crit damage (first hit is basically always a crit when sniping due to the sneak attack mechanic, and a crit from this will be 66 damage), the massive clip size (this is probably the single most underrated weapon stat; this is the difference between life and death a lot of the time) and it's damage is beast vs. non-armored pack-like enemies from the get-go. Only downsides whatsoever are that you'll want AT LEAST either Laser Commander or a crit build or it'll suffer vs. armored foes. Oh and of course you'll probably want to cope with the sheer weight of MFCs one way or another. But yeah, any character I have that uses THIS weapon? His survivability goes up three-fold. So deceivingly simple and cheap, and yet so undeniably powerful.

So there's my answer. How about yours? Which weapon do you consider to be -the- most overpowered storm of death the game has to offer?

Esther.

9k damage don't lie.

A Light Shining In Darkness.

When I first saw Graham use it, I thought it was just his skill was OP, but once I used it...holy toledo, I was ripping through all sorts of hostiles from Geckos to people to even Sentry Bots!

As much as I like ALSID I have to go with the modded .45 SMG if you have the Grunt Perk. I've always found that one so overpowered that I only use it to kill She then I pack it away.

From extended range, I'd say the Anti-Material Rifle firing explosive rounds. Shoot at 2 deathclaws standing close to one another while you're hidden and you can kill them both with one shot. You can kill a third while he's charging you. If you have a good line of sight, it can even be used against Cazadores as an area efect weapon that can kill most of them before they get too close; you and your companions can clean up what's left. From up close, I'd go with the riot shotgun, particularly with the "Shotgun Surgeon" and "And Stay Back" perks. It'll knock down anything it doesn't kill outright. If the target's lucky, it'll get back on its feet just in time to fall again for good.

The AER14 prototype laser rifle is OPed i my opinion. It has double crit % chance, so with the right perks you can have a 75% crit chance outside of VATS with it. Though it uses 2 cells per shot like lots of the more powerful laser guns.

The plasma caster i've also found to be insanely overpowered as well.

Sniper rifle with high level sneak and guns.