Another one hard to categorize. Does it really fit the "tracked vehicle" class?
Meet the Tankchair :

("Tankchair is for outdoor use only because it is so powerful it can ruin carpet and walls..." - Liz Soden, the person for who the Tankchair was first made)

Made at first by a husband who wanted his wife to be able to continue to hike with him and their kids after an accident...

It has know a "sibling": the Speedster

(motorcycle tires; speeds up to 30 mph...)

Which class for this one? 6-wheeler rocket?