GuNNER

GuNNER is a gun. It fires golden bullets, which make a red skull effect when hitting an enemy.

While holding GuNNER, whenever the player takes damage, 40 ammo is drained and a blue skull spawns nearby that disappears after a few seconds. Picking up the skull heals the player. If damage is taken while the skull is out, it will disappear. If the player does not have at least 40 ammo, the skull will not spawn.

Trivia

 * This gun is a reference to the game GoNNER. It functions very similarly to the game's health mechanic - upon taking damage, the player loses their "skull", weapon, and backpack, and can pick them back up for more health.
 * The Whale of a Time Synergy is a reference to Sally, the helpful whale at the end of each of GoNNER's stages. The skulls spawning with any weapon is most likely a reference to how Sally gives the player health upgrades at the end of a stage.