Sparky - Pikachu
Zippo - Charmeleon
Happy - Butterfree
Cruise - Pupitar
Rose - Taillow
Eevee - Mentioned in the dub, dunno if this counts.
Spearow and Tentacool were also among his Pokemon, but they weren't given nicknames, or at least they weren't mentioned to the public.
Edit: Oh, and if you count the Electric Tale of Pikachu Ritchie...