Looks like nobody has claimed this yet so I'll add: heavy equipment (excavators, loaders, chippers bigger than they had in "Fargo"...). Began as a solution to the "can't find a contractor to dig that hole" problem but like most things turned into an interesting rabbit hole and money pit. Interesting social side in terms of learning how to deal with mechanics, parts suppliers, welding, hydraulics, getting to know your way around a gravel pit.