Oh yes! Why did I forgot about these two! D: .. I mean they were absolutely fun to battle with! ..The 7th gym leaders, in R/S/E, Liz and Tate. They were ultra fun to battle IMO, I like hard battles like those (I beat em without surfffff<3).
Blaine has always been my favorite, probably because I love fire types and Arcanine :3
I voted for Wattson because he gave me the most fun battle. It was truly a well-played bout, I had to use every trick my admittedly limited Pokemon had.