Laser Machinegun

It does not open at full speed. Hold the button and the gun winds up over roughly the first two seconds, then settles into a solid stream. Tapping it throws the weapon away, because every release drops you back to the slow opening shots. Attack speed modifiers do nothing to any of this, so the wind up is fixed no matter what you are wearing.

The lasers scatter, and they stop dead on blocks and on the first enemy they touch. Against something huge you will never notice, because the whole cone lands. Against a small, mobile target most of the stream goes past. That makes it excellent on Duke Fishron or the Empress of Light and unreliable on the Lunatic Cultist. Standing hard against a single block wall lets the spread find its way through the gap.

Damage is locked in the moment you start firing. Picking up Mana Sickness partway through a stream will not weaken the lasers already coming out, and a damage buff drunk mid stream will not improve them either. Time your potions before you open up, not during.