With the commando perk the 10 mm on automatic with double the fire and a silencer. I use it as a mini uzi. Not great range but can fire it all day at medium distance. And a combat assault rifle with exploding shells. I try to conserve the ammo on it and try not to hit friendlies.
My plasma-shotgun with exploding bullets , I dubbed "Supernova"
http://images.akamai.steamusercontent.com/ugc/387670184648927225/34023F6547FCF44E2342A5E588191BDDD878F6E8/
And, Overseer's Guardian. The ultimate sniper rifle.
http://images.akamai.steamusercontent.com/ugc/387669574556216761/DAE907205CD45FF4494509B84C5803A85A06BE29/
Honorable mention would be Lorenzo's Artifact.
Level 36 and I'm still loving my Spray and Pray with the explosive rounds, the Two Shot .45 revolver, and the Overseer's Guardian (2 projectiles per shot semi-auto sniper).
In my opinion, Deliverer is the best standard ammo pistol in the game, when fully upgraded. Plus it looks hilarious when you use it while wearing power armor, because it's so tiny.
Beyond that, I like plasma rifles, but the ammo is too scarce to use it too often. I have a .308 rifle that's pretty great too.
The .44 pistols are pretty great when upgraded too.
i almost exclusively use deliverer but i have an explosive silenced 10mm called dollar that i love for being my main weapon for so long and a snub nosed .44 is probably the 2nd most stylish weapon in the game (after deliverer of course) and it packs a damn good punch
i have 2 saves and they both play very differently my first one, Larry, is all about his rifles and 2 handed weapons not including big guns and my favorite gun for that file is probably either my legendary assault rifle fully modded with a silencer and a reflex scope, legendary bonus giving you a damage buff if the target is at full health. (i personally like the reflex more than the actual scopes.) or the righteous authority i know its not the best laser rifle but idk its just never let me down its always been my go to since much earlier in the game and if you upgrade the critical shot damage boost perk in the luck tree its critical hits are outright OP'D.ive been able to one shot death claws with a critical hit fully upgraded critical hit perk in the head consistently.
but my second account , Big Brody, is waaaaaay more fun to play as. i made him a living breathing tank, upgrading damage resistance, life giver perk, unarmed perk upgraded all the way, blitz, and ricochet, big Brody is an absolute beast, able to take massive damage and beat you to death with his fists and melee weapons. from big brody id have to say my favorite weapon is my legendary death claw gauntlet, with the extra claw and the legendary bonus giving 50% more damage against super mutants theres nothing i haven't been able to kill in 1-3 swipes yet. I've killed a behemoth while high on psycho and med x, and having the unarmed perk upgraded to the second star in roughly 10 swipes. although i must admit the furious fist from swan is a VERY close runner up, its just so satisfying!
I can't really pick one. I generally carry a .50 Cal Recon Sniper Rifle, a short scoped Marksman's Calibrated Powerful Combat Rifle, and a glow sighted Marksman's Calibrated Powerful Combat Shotgun. Just recently I've started carrying Kellogg's Pistol as well, which is pretty nice.
This^
Its VATS cost is stupid cheap. If I have a Crit charged, I can use it, then recharge it again for another crit in one go with VATS. Outside of VATS it's a beast: maxed out modding gives it like 110 sheet damage, but with Ninja, Mister Sandman, and Deacon's perk, you get a 6.3x damage multiplier for sneak attacks.
And keep in mind all of this is for a gun that uses measly 10 mm rounds - perhaps the most cheap and plentiful ammo in the game.