Oh, oh dear, my older games are filled with just terrible, terrible nicknames, that are now wasting away upon My Pokemon Ranch. I'll gladly list a few of the worst ones when I get a chance, but I'm doing Algebra right now. I do recall naming a Plusle after me and a Minun after an ex I had, and seeing those two in the PC made me feel sad ):
However, I remember an older friend who named his pokemon, "Fatass," "Dr. Gay," and "Dumbass"
I thought it was the funniest thing, when I was 8.
I also used to name Legendaries after Caterpie, or other such weak Pokemon. I thought it would be funny to see my enemy go, "LOL CATERPIE? OH SHI- MEWTWO????!????!?!?" but I was a child.