In cases where you only name one character, and you get to pick gender (pokémon trainer!), I always pick a female and I always name it Kirie.
In cases where you only name one character, and you are forced as a male, usually I just keep the default name.
In cases where you get to name multiple characters, I like naming the characters after characters from other video games, just for amusement. On one playthrough of Emerald, I named all my pokémon after other pokémon, but that got confusing so I never did it again after that. I'm rather fond of naming characters after the character of Lunar games.