If you're a Nikon lens collector, this monster might make your Monday a little more exciting. Up for auction right now is the Nikkor 2000mm F/11 C Reflex. Its current asking price is $25,000.
The 2000mm F/11 C is actually a catadioptric lens, which means it uses a combination of glass and mirrors for a "folded" light path like that of a telescope. These lenses often have a fixed aperture, which means that F/11 isn't a maximum of F/11, it means every shot will be at F/11, nothing bigger or smaller.
The lens itself is quite a collector's item, with fewer than 300 of them ever produced. This copy, however, looks to be pretty beat up, including what may be a bent lens mount.
Still, it's a piece of history and those never come cheap. You could always pick one up and put it on your second body. Your main lens can be the ultra-rare and expensive Nikon 6mm Fisheye, which was up for auction a while back. That way, you have both wide angle and telephoto covered nicely.