you mean, plasma? never got my hands on one. i found the gatling laser at the end but never had a chance to use it.
like i said, i find that the laser shoots too randomly, unless you mod it to be a sniper, in which case you can't CQC with it anymore. most fights later on are in close quarters, so the AR worked the best for me out of the .44 legendary revolver (so slow to fire, horrible scope), .50 incendiary legendary sniper (saved me a lot of trouble on a couple occasions, but only long range really, medium or lower i'd rather use the CR because of the RoF and excellent accuracy), sniper laser rifle @ 60 dmg, combat shotgun (i picked up a legendary shotgun, the Fusil Terrible, but the extra recoil makes it almost useless), minigun (only really good for 2-3 boss fights, runs out of ammo instantly), missile launcher (idk why, but i missed a ton of shots with this one) modded to 4 tubes.
the fatman is great, even too strong. i'm gonna be honest, i think grenades are too OP. kellog's boss fight ended with a couple molotovs, and not only are they strong (high initial damage, DoT, and large area of effect, with mobs running into flame like it's nothing), but the game floods you with them.
F4 has the same problems that F3 had; the game designers made it too easy, and steered away from anything which might make the game hard - for example, weight for bullets. Come on, i'm carrying 39 missiles; 600 rounds of 5.56; 1200 rounds of 5mm. a nuke launcher, 6 guns, 260 pounds of steel, and i'm still running.
i liked the glowing sea (was pretty easy with two Rad-X and one RadAway), but imho the whole game should be like that - dangerous. Death should happen often and you, the player, would need to learn many aspects of the game and story before you could beat it.
That's how games were in the 80s.