Turned the Overseer's Combat Rifle (2 projectiles per shot) into a .308 silenced sniper with a large quick reload clip....ultimate mid-long range sneak weapon.

While a .Gauss (or even a Legendary .50 Sniper) can have more damage per shot, a Combat Rifle sniper can lay down 10 shots (with almost no recoil) before either heavier gun can fire a 2nd stable shot). Also, .308 is cheaper and more plentiful than .50 ammo.

I hit level 89 last night on my current playthrough. Been using Overseer's Guardian since level 25-ish and have no plans to change.

Two of you? Sounds unfair.

Delivered 10mm pistol is my number one silenced. But my main gun is Overseer Guardian. Starts at 55-66 damage but improved to 103 with .308 rounds. Basically a one shot one kill on almost anything. Can b bought at vault 81 for about 1000 or so caps.

Wasting Combat Rifle with highest damage Full auto receiver, Standard combat shotgun with highest damage mods and quick eject drum mag. Silenced auto 10 mm pistol. I do not recall where I found the Wasting Combat rifle but it works like a charm and uses less ammo as it does bleed damage over time so even the toughest ones go down pretty easy.

What do you consider high enough?

With a decent stealth-sniper build I find a .308 chambered scoped, silenced semi-automatic combat rifle to be fine.
The big opponents just means you have to press the mouse button faster

I used to carry a small armoury of various calibre weaponry, now it's just the .308 combat rifle.