That sounds like "Angel with a Shotgun" by pure1magination. Summary: Bucky Barnes always knew he'd go down fighting. He just didn't figure it would go down like this. In which Bucky dies, comes back as Steve's guardian angel, and stays with him throughout the events of Captain America: The First Avenger and The Avengers
Summary: Bucky Barnes always knew he'd go down fighting. He just didn't figure it would go down like this. In which Bucky dies, comes back as Steve's guardian angel, and stays with him throughout the events of Captain America: The First Avenger and The Avengers
http://archiveofourown.org/works/2078838?view_full_work=true