The Sky Stunner is a magic item wich looks like a rocket launcher. It shoots heat seeting rockets at mobs or players. These will explode on impact, leaving a trail of red firework sparks behind.
The Sky Stunner does 18 hitpoints of damage and has an infinite range. When you look at an enitity and you fire a shot, the projectile will follow the entity till it explodes.
You used to be able to get the Sky Stunner from Enchanted Chests but it has been moved to the Tech chest.