A module that applies IO actions only to the specific player/physics item/whatever that triggered it. With this you could:
- Easily make a button or switch that heals/gives a spawn tag to/teleports/kills/etc only the person who presses it
- Create a trigger volume that respawns only specific items that fall into it (useful for condos/workshop maps with physics items and pits)
- Create a trigger volume that hides and disables physics on items that fall into it (useful for creating Portal-esque prop disintegrators)
- Unhide a picture of a scary ghost that only the person who triggered it can see
- Much more, probably