Heart Condition (1990)
http://www.imdb.com/title/tt0099750/
Synopsis (from IMDb):
A racist cop (Bob Hoskins) receives a heart transplant from a black lawyer (Denzel Washington) he hates, who returns as a ghost to ask the cop to help take down the men who murdered him.
This flick was recently brought to my attention and I rented it through Youtube...HOLY SHIT! You have two amazing actors in their prime stumbling through a movie that is equal parts Buddy Cop Comedy/Gritty Cop Drama/Romantic Comedy/Race Relations Drama. It's an insane movie that truly has you wonder how it got made.
Trailer