While Canon's 40mm may be the smallest full-frame AF lens, its real claim to glory is that it is one of the first two Canon lenses with a stepping AF motor, allowing truly silent autofocus during video. It enables smooth Movie Servo AF with the newest Canon DSLRs. Optically strong, too, with excellent SQF numbers combined with negligible distortion and light falloff. And the price is right.

$199, street.