Canon TS-E 17mm f/4L Tilt-Shift

It's honestly a little difficult to write a persuasive description for this lens. Not because it's not an interesting lens. Actually, it is incredibly compelling. The issue is that the lens is most compelling to those who already know they need it. (You know who you are, and you're probably not even reading this, because you already know you need the lens for your shoot)

The bottom line is that if you're shooting architecture and need the highest quality wide angle lens that keeps lines straight, this is the lens for you. Interiors. Exteriors. Houses. Cathedrals. Museums. This lens can make them all look great. The edge-to-edge sharpness is about as good as it gets for a wide-angle lens, and its ability to control Chromatic Aberration (CA) is unparalleled. If you like the EF 14mm, this will take you to the next level. We also like it for high-angle landscape photography to keep trees straight.

Yes, it's a little bit of a one-trick pony. But boy oh boy, it does that trick better than any other lens. At the risk of sounding self-serving, this is the perfect lens to rent if you find yourself needing high-quality shots of architecture.