Probably a tie between my Canon 45 tilt shift or the 35L 1.4. I use the 35 the most and the tilt shift second most. I LOVE being able to use the tilt shift for the purpose it was truly intended : to keep lines straight. It's been a life saver and also a fun tool for art, and I'm proud to know how to use it as opposed to faking TS in Photoshop. That lens is just crisp.