Some kids had train sets. Actually, I did but it bored me to death. One xmas I got a SpaceWarp. Sure, I started out building the basic design they gave elaborate instructions for, but I got bored with that pretty fast. By the time it finally got dismantled (when my parents moved, natch), I'd rebuilt it at three times the designed height, had created elaborate track-jumping, triple and quadruple loops, and more.
When I saw this reappear after years of being out of production over at ThinkGeek it brought on a wave of nostalgia: