I usually use adjectives for nicknames. For example, in my crystal team I nicknamed my arcanine Valiant, my snorlax Royal, my slowbro Sage, and my marowak Guardian. I also have named a zigzagoon (I'm restarting sapphire) Rush. I'm not really into the Japanese or anime nicknames because it seems unoriginal to me (that's just mah opinion, though, so don't yell at me xD ) I prefer nicknames that make sense, but aren't too obvious.