Unfortunately I have no photos yet but the Lionel four-truck depressed-center flatcar is a favorite. I have five; one stock as Lionel built it with the transformer (it needs the bushings to be complete although transformers are usually shipped with the bushings packed separately for protection and clearance issues), one with four two-axle trucks (the inner pair Andrews and the outer pair Bettendorf or Dahlman), one with two three-axle sprung Buckeye trucks, one with two four-axle Lobaugh Buckeye trucks, and one with four-axle Lobaugh Commonwealth trucks. All except the stock Lionel are two-rail and have KD couplers.
Note that as a kid I wanted one (every Christmas put it on my list ) but my parents could not afford one. My Dad worked at Sears hardware and would get my trains after Christmas, either customer returns or unsold stock that Lionel would not take back so my train Christmas would show up around New Years. One major exception was the C&O SW7 switcher, that showed up on Christmas day one year and was a favorite. Still is in a way, I have several All Nation two-rail ones now. Another oddity, one year I got three of the white milk cars and an American Flyer S scale tanker. Dad took one of the milk cars and removed everything from the floor up and mounted the AF tank body on it; it did not look to bad to a twelve year-old and I had a one-of-a-kind car that none of my friends had. Oh, and the road name on it was either GULF or SUNOCO that matched my Lionel tankers.