35mm Tilt & Shift Lens
I used a 35mm Russian made Tilt & Shift Lens I picked up on ebay about a year ago. Pentax has an old 28mm Shift lens that is on ebay now, more than twice what I paid for my 35mm. The pentax lens does not have the tilt function.
This lens allows changing the film (sensor) plane (like old view cameras) relative to the lens plane. The shift function allows tall objects to be shot without tilting the camera up, eliminating the leaning look. The tilt can be used to make the lens paralel to something (ex. a flower you can not get tha camera parallel to) so the entire object is in focus with a shallow dof, or make the lens not parallel for dof where you want it. This is what is used when you see photos taken from high up and the middle is in focus (gives the appearance cars, people, buildings are miniature).