I'm looking for this anime where this girl had like this over-powered revolver and it hurts her to shoot it. In one scene she runs out of bullets and has one as a necklace and she shoots it and kills the bad guy or monster. I can't remember what it's called.
You can see the scene below. The main character is hurt by the recoil from her handgun and is out of bullets. She uses the one on her necklace.
Gunslinger Girl (2003) by Madhouse Studios
Originally Gunslinger Girl was a manga by Yu Aida. It premiered on May 21, 2002, in the monthly shōnen manga magazine Dengeki Daioh.