I've always wanted the ability to have state-independent damage flashing in G/ZDoom. I've done several attempts at it, first originally a really, really garbage one using DECORATE and ACS, and now this much nicer (but jankily coded, not super amazingly great with ZScript at the moment) version that works with everything (god bless event handlers!) Be forewarned, it doesn't play super nicely with renderstyles (spectres only seem to work if set to Software fuzz).
https://youtu.be/DhtVmF2qqeA Exciting gameplay footage!!
If anyone's willing to make this less ass, I'd appreciate it.
**EDIT: Just fixed a bug involving it not working when enemies gain health**