Much as I love Live and Let Die and Nobody Does it Better, I think I'd have to go with A View to a Kill from Duran Duran, it's just such an awesome tune for a less than awesome film. Proved you could make a poppy Bond track.
Definitely a toss up between Live and Let Die and View to a Kill.. Both are great songs.. VtaK finally won me over as a Duran Duran fan (just in time for them to mostly break up for a while. LOL)