I choose Blaine, both for his awesome connections in the games, and his amazingly fun Quiz cards back with the Gym Leader expansion of the TCG. (Look it up!)
HA HA HA HA HA YES! #MissingNo Giovanni, because he's the father of my favorite rival. And because he's a badass. So is Silver, btw. He also uses Ground-Types, and some of my favorite 'Mons. And he appeared in Pokémon: The First Movie which was AMAZING! Edit: Blaine in the manga was SO COOL! I mean, that Mewtwo-cell-transference and Mewtwo-control thing was AWESOME! #MissingNo
Silver/Soul, from the Gold/Silver or HeartGold/SoulSilver games. It's eventually revealed that Silver is Giovanni's son, and he's trying to escape both his father and Team Rocket's influence on him.
I like Blaine, I think he's a tough person, continuing his duties as gym leader even after his gym got destroyed by the volcano.