Steam name: Roadsguy
Server: MCTTT (could also be applied to all Gmod servers)
Description: The ULX respond command is basically reverse admin chat. Used with a # instead of an @, it appears as "Admins to you: message" compared to "You to admins: message". Currently, however, once used, it is invisible to anyone but the recipient. Not even the sender staff can see it. (I tested it during my time as admin.)
This would be a great convenience tool for mods to use to message players officially, as it can also be seen by other staff. This way conversations between staff and players aren't just seen by other staff as solely what the player puts into admin chat. It's also more visible than psay, which can be useful in messaging players that pay less attention to chat.