I wonder if that Qatar sheikh is on FM .. you know .. the dude who had a custom CZ 1700mm lens made. Maybe he'll be kind enough to post some samples. Wonder how that lens takes a TC. Didn't find it on B&S yet .. he's still using it?
I've taken shots of the International Space Station with the shuttle docked with a 600L + 2x TC = 1.4 TC on a 50D. You can make out the shuttle docked next to the station but it's very small. I don't have it here as I am on the road but it was fun.
Physically widest lens? 4" reflector telescope w/ cam adapter. I suppose that would also be the longest focal length, around 1100 or 1300 mm, if I remember right.
Widest angle? 8 mm circular fisheye (Peleng, which I sold not too long ago).
Widest rectilinear coverage? 12 mm Voigtlander (on 35 mm film).