Colress in the Plasma Frigate? Holy shit. He had a Sturdy Magneton with Thunder Wave, and at the time I hadn't stocked up on Paralyz Heals, so I went through that entire battle with my Magnezone getting parahaxed at every other turn.
Also, HGSS Whitney's Miltank was hell. I had a female Geodude so all it could use was Stomp, and I got flinched almost every single turn.