(See the best response by DarkCampainger.)
switch(alert("Do you wish to be revived?","","Yes","No"))
src.Dead = 0
usr.overlays -= /obj/Other/Halo
usr.loc = locate(99,99,1)

Problem description:
When a person is click and is dead, they goto that spot and there Halo disappears. But the location works but the Halo still remains as an overlay. When I add the Halo, it is in a proc. But when I remove the halo, it stays.
Best response
You're mixing usr and src. Unless the player is clicking their own mob, you probably want usr.Dead = 0. Otherwise they should all be src.

As to your specific problem, can you show us how you're adding the halo overlay?
Wow, I actually didn't see that. Thanks.