I think SMF users and admins will get a kick out of this one. LOL
Annoy User (http://custom.simplemachines.org/mods/index.php?mod=2232)
I've never had an occasion where that was needed, but I know it could be useful.
I just use the moderations for SMF 2.0 or visual warning for SMF 1.1.x. But it would be really annoying. LOL