I pedicab occassionally with a guy with some insane gearing. Pedicabs (good ones) have an intermediate drive, like a hub where the normal gearing is, and then a cogon the other side that goes back to the rear axle.

This guy might have anoter intermediate or something, bu he essentially has: MTB Triple chainring -> 7sp MTB Cassette -> Nexus 8spd (which replaced a 3 spd that he used to use).

Its pretty rediculous and obviously has a TON of redundant gears, but when it is in low-low-low... Lord, it could seriously pull stumps. You have to spin like 100 revolutions to move like 3 ft it seems like. Outrageous. I never have run out of gearing on my 21spd cab....