I don't think I ever call Pottie, Pottie... her proper name is Puerto Rico, stable name Pottie, but I either call her Pots or Small (she's 14.1hh).
Denys just gets called Chops (no idea why!)
Frank gets Frankie, Frankel or Frube (he turns pink when clipped so I called him a frozen strawberry frube at some point last winter and now I can't shake it!)
All get called Trouble...
Oreo has a lot! At the minute its mostly cash cow! As she has cost a lot in vets fees through self inflicted injuries (which have rather suspicious timings!). Also donkey, gorgeous, twatface and a few ruder ones