Tamron SP AF 10-24mm F/3.5-4.5 Di II LD Aspherical (IF)
Usefully it's sharpest at the wide end, which is of course what users will be buying it for, although it's no slouch at longer focal lengths either. And while the extreme corners are rather soft, this only affects a very limited region of the frame, and on those rare occasions where it's really a problem, only a slight crop is needed to deal with it.
A crop-sensor shooter looking for an ultra wide angle with a versatile range - especially for architecture and landscapes.
Users who shoot often in low light environments.