Very good guys up to now. But I got you all beat. My vote for the most oddball freight car with absolutely none built as a prototype is........................The MTL giraffe gondola cars.
Yeah, nolo contendre. There were only three of the 1958 Buick looking LWT 1200. But three is three...
How about the snow plows made by More (Japan)? Seemed to have been expensive relative to (say) locos when they came out, looks nothing like most US prototypes AFAIK, yet still gets snapped up on The Bay for real money. http://www.visi.com/~spookshow/ccmoreplow.html
I'm still lovin' the 94' A1G Atlas tank. Another thing is that the ideal car should be something that only the N scalers got gifted with.... not a 'me too' from the HO side. Something the HO guys can look at and say, hey, how come they only got it? We had another thread a while back on the giraffe gondola. I know I was stunned to discover that there actually were giraffe circus wagons where the head stuck out the top (or at least could), and those wagons were rail-loaded (with the giraffe in them) so it's not as absolutely crazy as I thought. So it's possible at least the IDEA came from seeing that in a circus train. I have no evidence of the heads were ever up in transit, but seeing the circus wagon in the Baraboo circus parade with the giraffe sticking out of the top made me quiet down a hair on that particular foobie. I used to bust on flatcar loads of airplanes and boats until a friend of mine showed me those loads on the Alaska RR.
It's a track inspection car and I did get a picture of it in Colorado back in '98. I later saw an article or at least a description in Trains. Don't have the photo in digital or even know where those photos are, however. Echo "DDOOOHHHH!!!!!"
The More rotary is more like the European and British stuff sold by Lima with American roadnames, in their proper context they were not rare or unusual prototypes just painted in fantasy roadnames. If we include those we could add most of Con-Cor's locomotives and a good percentage of Micro Train's output. The model is of a real Japanese prototype. I took the photo below of a rotary on display that looks pretty close to the More model from a train on the way to Wakkanai, the northernmost point of Hokkaido, in 2010. It has a different tender but probably picked up a replacement one from a retired steam locomotive sometime during it's career, it looks to me like a D51 Mikado tender.
Ultrasonic rail detection car. It's not as streamlined as the Bachmann one but I spent a day driving this one around Brisbane a couple of years ago.
If you want some REAL fun, you can buy the prototype..... it would make an interesting lawn ornament or cabana: http://www.railmerchants.net/up-ec2/index.html Wow, it even comes with all the original operations manuals. Only driven by a little old track inspector who used it to check out the Centennial branch on Sundays. I see it's numbered EC-2, so that means, presumably, there were at least TWO of them, so the 94' tank is still unmatched!
i seem to remember seeing an 89foot stock car "PIG PALACE" or something like that offered by atlas back in the 70s cant be too many prototypes for that one out there.
The "Pig Palace" was a NP prototype. I am not sure how many were made but if you find one of these models now you are going to pay a pretty $$$$ for it.
"I see it's numbered EC-2, so that means, presumably, there were at least TWO of them,..." Actually three... http://rrpicturearchives.net/showPicture.aspx?id=1110508 http://rrpicturearchives.net/showPicture.aspx?id=1847964
I think the first one was built in the NP shops from a bash of two 40 foot newer stockcars, was listed as an 85 footer. I believe Ortner built the rest for a total of 21 or 22 cars. I actually had some of these up until about 2000 when I got rid of a bunch of cars too modern for my era.