Prime Laser Arm

Info
A magic weapon obtained from destroying Skeletron Prime's Laser Arm, has a 1/25 chance of being dropped. This weapon is similar to the Magic Branch in that it takes no mana to use. The Prime Laser Arm creates light when fired, but has no visible projectile. It has a range of around 18 blocks. Its best modifier, assuming it retains the standard game rules, is Godly, as it costs no mana to fire. It is unknown if it fires multiple projectiles, but it appears to pierce up to three enemies.

Trivia
"Imma fire mah Lazoh" is an internet meme, said by Shoop Da Whoop in "The Lazer Collection" series.

The Laser Arm's damage is actually fairly low for a hardmode weapon, being below even the Laser Rifle in base damage.

Your character will appear with the arm equipped even when not firing, if it is selected on the hotbar.