Hmmm during the days when I was playing Fallout 3 and New Vegas on Xbox 360 I mostly used assault rifles till New Vegas came around I would use the Marksman Carbine throughout the entire playthrough. Also if I ran out of ammo I'd use the .44 Magnum as my sidearm in Fallout 3 and when the DLC Honest Hearts came out I started to use the .45 Pistol!! Which I still kind of use today, modded now.

These days I still use assault rifles but modded of course. Mostly M4 types.

Anything really, depends on my situation. Pistols, shotguns, smgs, assault rifles, sniper rifles. What I need when I need it is what I use. Actually really anything but heavy weapons. The idea of using miniguns and/or rocket launchers never really sat well with me. Don't get me wrong I still will use lmgs if needed but I don't really care for anything bigger.

In New Vegas, the anti rifle, as long as it's not a boss like the Legate it usually one shot kills anything, at lower levels I use That Gun a lot. In 3 I usually just use the assault rifle, and since I use the Weapon Mod Expansion mod or whatever, it has a silencer on it as well, that works nicely, and at higher levels for things like hordes of enemies or bosses, a MIRV does the trick. That's just default game though, with mods I always look for an M4, that's one of my favorite guns in video games aside from the VSS, which sadly has only been a good gun in the STALKER series.

My favorite in F3 is the R91 assaultrifle, Lincoln's rifle (aka Slaver slayer), doublebarrel shotgun and of course the fat man!

In New Vegas i prefer the N99, 44 mag revolver and the tommy gun. Fat Man suks in FNV, low damage not enought ammo, almost i miss the R91, the most automatic guns just suks in FNV

m16-Betty
1911-bob

In Fallout New Vegas with the help from 'Old World Blues' DLC, I rather take LAER.
It's a powerful (energy) weapon.

In the vanilla fallout game probably would have to be the Brush gun, but modded I mainly use Millenia's AK-47.

Ranger Sequoia baby!

Even modded I enjoy the Brush Gun, Trail Carbine and Cowboy Repeater. Fun guns to fire. Modded, depends on the playthrough. Usually use a mixture of bolt action rifles, shotguns and a few revolvers depending on the situation.

For me I use all rifle type with scope for middle and long range shotgun for shot range. mostly I like shotgun so mush if I have "And stay back" perk it more fun to fire shotgun at someone.

My favourite vanilla weapon in New Vegas is the Ranger Sequoia and my favourite mod weapon is Millenia's PPSH.

That gun is probably my favorite gun to use, other then the hunting shotgun/rifle. And for melee i use a switchblade.

Probably the anti-material rifle, works in almost every situation for me in my opinion

I like the cowboy repeater because it has that western feel and the ammo is easy to come by, along with it packing a punch.

The hunting revolver, not the unique one, the one with the scope.

It's so powerful! It's a handgun that fires large rifle rounds! It's pretty amazing in my opinion.

I would say that I use the Spitfire's Thunder weapon mod. I always loved using the AMR, and when I found a mod that added in a unique one, I was overjoyed. I don't think there is any other weapon I have used more besides the YCS/186.

Probably and assault rifle of some sort but I use too many to really say one. But if I had to guess probably the AK-47 from AK & AR15 mod. Such a cool mod.

PSG-1

its really good for a sniper XD

Recently I have been using the Liberator rifle, decent damage and single shot so I do not burn through ammo.

the hunting rifle

and 10 mm pistol
but i use (my own) mods that replace them with

www.nexusmods.com/newvegas/mods/55948

www.nexusmods.com/newvegas/mods/49230