Speaking of early gamebreakers; it's quite possible to skip over to Rivet City and do the Replicated Man quest, and if you talk to the android [spoiler](who turns out to be Harkness, though you still have to go through the motions in order to get the proper dialogue choices)[/spoiler] you can convince him to give you A3-21's Plasma Rifle, which has even higher base damage than the normal plasma rifle and starts out fully repaired. If you make boosting your energy weapons skill a priority and bump it up to 75-80 ASAP (which is harder without the bobblehead, which you can't get until the end of the game because it's in motherfuck fucking Raven Rock) you can just melt everybody, though I'd save it for Deathclaws and Sentry Robots and other similarly nasty fuckers (the issue here being weapon health rather than ammo - MF cells are common enough, but actual plasma rifles aren't, and getting your PR fixed in a shop costs a great fucking shit ton of caps).
Or just drop by the Museum of Natural History and pick up Lincoln's Repeater, which is almost as fantastically powerful and can be repaired with common hunting rifles. Plus it uses the small guns skill which is easier to buff up because the relevant bobblehead is actually available without doing almost all of the main quest, though I forget just where it is.
