Yknow, I know that GGO's bullet trail is just a gimmick for a sword user to win in a gun world (SAO season 2), but I honestly like the Idea of the bullet trail. It would be fun to see someone using it in a world full of guns.
The HUGE problem is that there just isn't a lot of fanfic worthy worlds with guns as their primary way of fighting. I can think of a few likr Halo or Fallout (RWBY also I guess but they have dust), but I can't think of any other. Maybe also count it for physical attacks? But I feel like that is literally just sharingan with reduced powers.