Isoblaster
Isoblaster is a rare one-handed pistol.
A blaster meant to spread 
isoslime everywhere. Holding LMB will charge up an isoslime ball.
Can be upgraded to 
Isoblaster Prime ★ at the Weapon Upgrade Anvil.
Ingame
Radiomessages on pickup:
- You’ve just picked up an alta weapon, or an “energy tool”, as they call it. According to my database, these usually have an extended set of features. I suggest reading its description.
Sources
Found naturally in containers:
Can be bought from merchants:
Can be obtained from special items:
Can be obtained via 
Spawnable Item Pack or 