Nyeb said:
I have to agree on the hunting rifle as the most useful, but word of advice kiddies.
Go to the Republic of Dave and kill Dave. Unlock his safe and find 'Ol Painless. It's a hunting rifle that does a little more damage. The only downside is no more of Dave's Republic. Worth it, for a more powerful useful weapon.
Or you could I don't know do the quest and tamper the vote. He leaves, and you get permission to loot the place.
I would say firebrand, a crit hit pretty much one shots anything. Crits nearly every shot. Downside is that it rarely pops up, and you can only find two alien blasters in the game (which are the only things to repair it with) and I have only found about 240 ammo for the thing the whole game.
I guess my fav would be Vengeance nearly every group of super mutants has a gatling laser or two with them, ammo is everywhere and can be bought. There is nothing like raining destruction down with Fawkes in tow using a gatling laser as well.
Then again the Gauss rifle is my favorite to cruise around the wasteland with, I get it repaired at Haley's with the glitch there.