...The new Lincoln's Repeater.
Easily the best ranged weapon one can get their hands on during the first 30 levels. Didn't care much for the stock configuration, but gun nut 3 sorted that out quickly. It's a combat rifle that does 2x the damage in practice. Defiantly a gun one should consider rushing to get ASAP. Just need 3 fusion cores and 3k caps worth of barter at the most, much lower if you are a charming waster. I bluffed my way into vault 81 and did the trade with 11 charisma + trade perks.
.38 ammo exchanges to caps at a 1:1 rate FYI. Hoard that stuff.