I usually don't give my Pokemon nicknames, but I have:
Sudowoodo: NowhereMan
Geodude: Banana~ (I don't know how that happened. P: )
Miltank: Meushi
Sentret: Cookie
Smeargle: Sutcliffe, Astrid, Crayola, MS Paint, Andy (someone asked, xD), Easel, Paintbox, Smear, Apollo, Mona Lisa, Rihanna, and...