I'm going to have to go old school here, my Lionel 675. It was one of my grandfathers trains and the first one he bought after the war. It still gets a small amount of running time on the layout when ever I have it out. It took a lot of beating when we were kids and it still runs like a champ almost 70 years later.
Jerry
Well, Jerry, had I not seen your post, I was all set to say the 1973 Southern Crescent set I got as a toddler. That thing was beaten on and beaten on for years. Dropped from heights, kicked off the track several times by my older sibling to **** me off. Stored and kicked under the bed, hidden from view like an ancient artifact in dust bunnies, never ever lubed. Mom found it about a year ago and brought it up on her visit. We put it in the track and voila! Runs just fine.