Bicycles! I ride my mountain bike pretty hard any time I go out for fun, and sometimes come back with an out of true wheel, a screwed drive train, bent derailleurs/disc brakes/frame/etc. This got in the way of my daily commuting/exercising so I decided I needed to have a good road bike, and a spare cheap mountain bike to make sure I can still go out to have fun, even if my primary mtb is in the middle of surgery. Having three bikes also means that when friends are in town visiting, I can show them around the city without having to resort to expensive taxis/zipcars or public transit.