i know this topic has been covered before with reference to nicknames for our customers so here are a couple of ours
FRIDAY MAN
(cos we clean his windows mon/tues and he always says "can i pay you on friday")
SKIRTMAN
(cos he always comes to the door wearing a kilt and he's not scottish)
TASTY
CLASS
(these 2 are both females so i'll leave it your imagination as to how the got these names)