I thought I only had a few cars that would fit this category but I realize I have more than I thought. These are in no particular order but I have quick access to pictures of this batch. I'll dig out others and post pictures of them as they come available.
This is a METCA offering. I saw a picture of it somewhere and it caught my eye because my dad worked for Metropolitan Roofing Supply in the Bronx for 30 years. They manufactured Durex roofing cements and sealers, contracted with other big manufacturers to produce their roofing cements and sold every type of material, supply and equipment for any type of roof system. Their fleet of delivery trucks were green with a gold MRS in a diamond emblazoned on the doors. I could see their boxcar, if they owned one looking very much like this. Alas this model was no longer listed on the METCA web site. I contacted Stu to see if any were still available. To my dismay Stu said if it's not on the web site it's out of stock. The next day I received an e-mail from Stu. There was still one left, the one used for the METCA display, if I was interested. So now it's mine.
19192 Lionel Collectors Club of America NASA tank car. An eBay purchase.
I had one of Jim Sutter's Weaver Genny Light reefers and was looking for a Genesee one to go with it. I came across this LOTS offering on eBay for a reasonable price considering the prices of other Genesee cars available at the time.
This K-Line Ewing Oil tank car is stunning in green and gold and just happens to be a TTOS chapter offering from 1989.
Nassau Lionel Operating Engineers 2006 boxcar celebrating the 80th anniversary of LIRR 401, the world's first road diesel. This one came from Trainz. As did the LIRR flat with Tomcat trailer from NLOE already posted by Bob, @RSJB18.
I also have a single offering from NJHR, the Schmidt's reefer already posted. I bought at one of the Trainstocks, I don't remember which, and Ben, @bluelinec4, was nice enough to give me the preorder pricing even though I hadn't pre-ordered it.
I know there are a couple more NLOE cars and a St. Louis club car that I need to get pictures of and maybe another one or two I'm not remembering. I've also got some K-Line Collectors' Club offerings that I believe went from KCC offerings to inclusion in catalogs for general sale. I'll gather up some pics of those and post those separate from other club oferings.