Canon 50mm f/1.4
Roaming the streets of London with this lens is tantamount to
cheating, frankly; it's such a beauty that it's nigh-on impossible to
take a bad photo with it. I'll keep trying, though, obviously.
Oh, and in case you wondered, the camera body is a 450D.
Photo taken with my iPhone, and slightly desaturated in Photogene (the iPhone app) before uploading to Flickr via e-mail to my TOP SECRET UPLOAD VIA EMAIL address)