Pokemon that I know of that appear are:
Jolteon
Vileplume
Breloom
Electabuzz
Can't really remember all them. They usually give you a status condition, most of them being paralisis. But don't worry, you'll find many Cheri Berries, and some Lum Berries.
Like Jc said use various types. But that's not really a good answer.
The brain uses the three Regis the first time, and the second time he uses the three legendary birds. So keep that in mind.