Dunno what the "hottest" is...
Out of what I've heard in the last little while that would be considered "hot"...I'd have to say Akon's "Smack That" is the last one that's tickled my fancy (although there's proabably a lot better out there I haven't heard).
...and although I love(d) MIA, I think Bird Flu might be one of the most annoying songs I've ever heard in my life.