So I just bought a used Rio Grande alco A-B-A diesel by American Models. I really like the yellow and black "prospector" coloration scheme, and I have been after this diesel for awhile.
American Models is a company that specializes in making S scale locomotives and cars. They do a good job with the detail and all and they run nicely, but the frustrating thing is how they do limited runs of all of their stuff, and once they sell all of a model, they retire it and never produce it again.
I also found a used American Flyer alco A-B-A Santa Fe in the red and chrome coloration for ridiculously cheap. The body of all three units is in very good shape and no rust on the chassis, just that they have been sitting on somebody's shelf collecting dust since the early-1970's. It runs, but very poorly. It probably just needs to be cleaned out a bit inside. Luckily, I know a guy who repairs trains and is pretty reasonable, price-wise.
For those of you who live outside of the US, are there any foreign companies that also make stuff for S gauge? It is larger than HO, but very detailed and well proportioned. O gauge is slightly larger, but I never could get past the strange-looking third rail for O gauge track.