Charlie is a mask in Hotline Miami. Charlie is a mask of an octopus and when worn grants Jacket a passive ability of causing more melee weapons to spawn more often in weapon spawns. In Hotline Miami 2's Level Editor, the mask gives no perks as random weapon spawns aren't in Hotline Miami 2's code.
Although this mask increases the frequency of melee weapon spawns, it appears that only the basic set of melee weapons spawn under the influence of this mask. Even if the player has all the melee weapons unlocked, none of the unlockable weapons will spawn. Ironically, this effect makes Charlie the single most useless mask for obtaining the Always on Top and Knife for Pros achievements.
It is possibly the Technician's mask.