The easiest answer is "It depends on the era in my life" Early on I used my collecting energies to collect American Flyer S gauge trains and accessories. (My father and older brother designated an S gauge train for my use.) I "limited" myself to the 3 digit era and collected one of almost everything with 3 digits. The next era was to collect a "few" pieces to go with the 3 pre war American Flyer O-gauge sets and one AF Wide Gauge set that were in the family before I was. That era has morphed into collecting anything American Flyer O or Wide Gauge. I "limited" myself (please don't laugh) to cars with 8 wheels and as many variations as possible. This is by far the largest segment of the collection. The collector gene that I bear has driven me to have "a few" representative examples of American Flyer's competitors during the pre war era. So the collection also has Ives, Dorfan, Marx and of course a smattering of Lionel. I consider myself a collector who is building a research library of toy trains. You will find most of my offerings to this site in the tinplate section. I also have posted photos of pre war American Flyer Trains for almost 12 years over on the CTT site. I enjoy "playing" with my trains, answering questions, and doing research and writing.
Thanks for asking and starting this thread.
Northwoods Flyer
Greg