Not necessarily my top five, but here are five who have not been mentioned that I think deserve a mention (and the first three are certainly top-five contenders in my book):
Larry Graham
Miroslav Vitous
Donald "Duck" Dunn
Klaus Voorman
George Porter Jr.
Honorable mention: Derek Smalls
Larry Graham
Miroslav Vitous
Donald "Duck" Dunn
Klaus Voorman
George Porter Jr.
Honorable mention: Derek Smalls