Ones that are ez to get are corrupt light, it's quite ez to max, starts at rare, and if you have good elec cap and regen, though I don't recommend it, flaminator, also starts at rare, anything else that's good start at epic, such as desolation, savegery, magma recoiler, basalt dissolver, note that the two last ones are more support type weapons, but useful nonetheless, if you can farm last boss on normal you should get some good stuff after a while, if you can't do that boss do any other boss, the harder the boss the better the rewards, but if you can't do it safely, safely bieng that you finish on auto with enough hp