O Scale. O scale is 1:48 in the US, you will find a few variations around the world. When you think of O Scale trains, you naturally think of the classics like Lionel, American Flyer, Marx but there is so much more available. For years, O scale was the king of trains and they were loved and played with by young ones for years. While their size may make setting up a railway with enough running track for your taste, many have filled their basements with incredible layouts. Many clubs also go to great lengths to create some super detailed layouts that run well and often.
O Scale can be quite collectible as well. As mentioned earlier, these trains were typically played with hard for years so finding pristine pieces can be a challenge. If you remember the Adams Family, Gomez routinely crashed and blew up his trains. I am sure many young ones enjoyed doing the same.