Here is one I saw long ago >> 20 years on TV, probably a “Creature Double Feature”. Hippy dirtbag guy finds this alien weapon. He puts his arm into it and has a good time blasting stuff with the laser pulse. It may have impregnated his palm with some sort of thing (maybe a gem or a scab). Eventually he loses his humanity to the weapon and he becomes an alien (after he finds that he can no longer remove his arm). I remember him blasting stuff like telephone poles maybe. Gun looked like a tube that you stuck your forearm into…poor bastard.