Sigma 14mm f/2.8 EX HSM?
 

I'm probably late to chime in here but I own the Sigma 14mm f/2.8 EX HSM for Nikon that I use with my Sony EX1 and Letus extreme. I love this lens. I have noticed it can get a little soft on the corners in some shots though. I will be trying it out on a friends Canon 5D Mark II (with nikon adapter ring) next month in Vietnam and Angkor Wat so maybe I can post some shots here if theres interest.

This lens stopped being made about 2 years ago but can be found on ebay for between $450 and $600 US. I see they made a canon version too. Heres one review. Sigma 14mm f/2.8 EX HSM Lens Reviews | Canon-Reviews.com

alex