I'm just young enough to post in this thread, but just old enough to have received a Marx windup set as my first train when I was a kid.
I collect O gauge windup trains, and have a windup train layout that is meant to display the vintage mechanical trains and the accessories that go with them. There isn't any electric power to the track... it isn't needed, nor is the middle rail. You can see a good portion of my windup train collection on the shelves around the layout. I primarily collect Marx trains, but also have clockworks from Ives, American Flyer, Hafner, and even a few Lionel:
I've also been involved in 12" gauge outdoor railroading since I was a teenager. I have a 12" gauge railroad on my property, with a few locomotives to pull the trains: