What weapons are worth upgrading?

[Lord of D:]

Im aware that the Autocannon that you get later on its the best weapon of the game, and also that the pistol and machinegun you get at the beginning are easely outclassed by others, so i was wondering if the shotgun and sniper are worth upgrading, along with later weapons i may find.

[GreyVixen]

The shotgun is worth upgrading a little, but once you get the autocannon there's little reason to use it anymore

[damian2472005]

shotgun anyway also sniper rifle for sure the rest as you like.