From Gamer Heroes: “Remnant From The Ashes has quite a few different weapons to be found in the game. Some are easy to get, and others are hidden behind locked doors or chests. Check out this Remnant: From The Ashes weapon location guide to find them all.
Its worth noting that many of the guns are hidden away behind specific bosses. For example, on Earth, you will either fight the Ent or the Singe boss. Both drop different weapons, but you can only fight one on a single play through. You can reset your world for a chance to encounter another, without losing your character or items.”
Source: N4G PC Remnant From The Ashes Weapon Location Guide