Originally Posted by distortion
It's Danny St. John's weapon of choice. The same gun he used to kill Jolene. If you speak to him after the reconnaissance mission with Lee he'll show his "affection" towards the gun.
"I'm glad I got to you her today... my girl here."
"You uh, really like that gun."
"What's not to like?"
"It's just a gun..."
"That's where you're wrong. This is Charlotte. She's as faithful as a starvin' hound when you got a bone in your pocket."
After deciding Danny's fate, Lilly takes Charlotte and brings it back to the motel. It's the same gun Lee uses when he was defending the motel against bandits and, later, walkers.