I don't think much about nicknames. I usually name them random things. Like, I bought HeartGold this Monday and named my Totodile Eliminator for some reasons. And in my LeafGreen, I named Bulbasaur Bianca. I often name Ratatas Ralph and Zubats Sucker. I never use something personal. Used to name Zigzagoon after my dog though. It kinda reminded me of him.