For arrangement, I would have to go with Jean-Michel Jarre. "Rendez-Vous" from 1986 is a trip.
Suzanne Ciani for '85s "The Velocity of Love" is also a winner. I guess Synchestra is also there.
I emphasize on new age artists for keyboards because that's the emphasis of that genre of music.
For rock, I guess I could say Alan Fitzgerald from Night Ranger has some memorable bits.