Wolverine by Jason Aaron: The Complete Collection #1

Wendell is a small, average man with a pitiful life. Every day he goes to his job, sitting at a machine gun and periodically shooting a hairy, feral man in a pit to keep the savage mutant's healing factor in overload so he cannot escape. Wendell's life is not all that great but he manages to keep it under control. That is, until the man in the pit, the man he continually shoots day in and day out, starts talking to him.