Sometime last year, I got the Rokinon 12mm for Canon. This is an ultra wide / Fisheye lens with a 180 degree corner to corner field of view, and manual focus. I primarily got the lens because my Canon 16-35 wasn't cutting it for star field photography - it gave me the wide angle to get much of the milky way in but the apperture was too small, requiring longer exposures. Since then, I've discovered you can have a lot of fun with such a wide lens - even if you can't use filters (because of the protruding front element), and even with manual focus.
On my most recent trip to New York, I took this lens, expecting to get some interesting city scapes. It delivered on that, but where it really excelled (to my mind) was in interior shots of some new and old NYC landmarks.
"Rainy Times Square"
"View from Hotel Window"
"Grand Central Station"
"Ceiling, Grand Central"
"The Old Gods and the New"
"St Patrick's Cathedral"
"Evening Commuter, Grand Central"
"Transportation Hub, World Trade Center"
"Brave New World"