If you're thinking of a higher-level creature, it'd be interesting if it was drawn in by gunfire and would attack on seeing someone holding a gun out in the open.
It would have to be somewhat hard to see before it approaches you, and spawn rarely, but it'd be an interesting dynamic and probably very frustrating for people who like to empty all their bullets most of the time when they don't need to.
In addition to this, all the animals that are currently in the game should run away as soon as they hear gunfire.
love the idea, I think a monster to something like off of the movie Jeepers Creepers. A fucking big flying man Bat preying on people. This would scare the shit out of me, if I was running through a forest and heard a scary ass screeching in the night sky flying over me. Or if this thing landed on top of your base and started scratching and clawing. Just my thoughts.