Hot wheel sets are a staple of many a childhood, but they're also a staple of creating a huge sprawling mess that someone will inevitably trip over and start cursing. So! Take that racetrack off the floor and put it on the wall.
Hot Wheels Wall Tracks are (gasp!) tracks for your wall, stickable using 3M adhesive strips, and packing all the zany flips, curves, and loops of the horizontal equivalent. The vertical courses, available in the fall for 30 bucks, can even go around corners, and once you reach bottom, can plug right in to the traditional Hot Wheels floor tracks you might already own. Anyone with a cramped apartment or bedroom lacking in floor space would have a blast with this, even if it lacks the normal round and round aspect of a floor race. But who cares! Watching a car plummet to a destructive end is way more exciting. Just don't stick the tracks over any emergency exits or something.