Some of my favorite soundratcks: Garden State, Walker
Best rock song written for a movie might be Let’s Go Crazy from Purple Rain. Though I love Queen’s Flash.
Best use of an existing song in a movie: 25 Miles by Edwin Starr and Gimme Shelter by The Rolling Stones in Adventures in Babysitting (outstanding soundtrack), and Sister Christian in Boogie Nights.
Best score… hmm… The Good, The Bad & The Ugly or The Untouchables. I don’t know if any films have been better scored than those, the music was not only beautiful (The Untouchables) and cool (GBU), but perfectly fit the scenes.

Worst: Anything be the aforementioned Ms. Dion. Anything by Christopher Cross (Arthur’s Theme).

Of course, the all-time best movie music: Everything from Breakin’ and Breakin’ 2: Electric Boogaloo.