"A Change Is Gonna Come" by Sam Cooke, number one. I can't hear it too much, because it tears me up every time I hear it.
I dig most of Rick James' funk rock, but "Bustin' Out" always gets me going.
I also love most of Earth Wind & Fire's work, but "Reasons" has to be my favorite.
I love everything Funkadelic does, but "One Nation Under a Groove" is great.