gunshot; bullet
Literally a bullet or shot from a gun; can refer to the projectile itself or the act of shooting.
The bullet hit the wall.
messenger who doesn't return; one-way messenger
Idiomatic: a person sent on an errand or mission who is not expected to return, like a bullet once fired. Often used in underworld or dramatic contexts.
He was sent into enemy territory as a one-way messenger.
bull's-eye candy
A type of hard candy with a bull's-eye pattern, named after its resemblance to a target or bullet hole.
I bought some bull's-eye candy at the cheap sweets shop.