I keep having to check - a lot of posters are looking for MTH and Lionel here on the 2-rail forum. I think that is great - about time Lionel started again making 2-rail stuff.
I am overwhelmed with trains, but would not mind seeing a Harriman 0-6-0 in die cast with a round boiler. My favorite is the SP S-9.
I would think that most of the above wants have been done at least once in O Scale, especially all those Diesels with numbers between SD-9 and SD-45. There are probably more Warbonnet PAs in O Scale than there are NYC Hudsons.
We have abundance!