The new Canon 24mm and 17mm TS-E lenses. Both are razor sharp and employ Canon's subwavelength coating to reduce flare. The coating may be responsible for the etherial diffuse colors seen deep inside the lens elements.
A lens as wide as the 17mm can only be used in very specialized photographic situations. Filters and lens hoods cannot be used, but the lens is remarkably free of flare spots without one.