There are some related threads but I wanted to consolidate information into one place without threadjacking regarding this question I pose which is, “What are the best unicycle candidates for riding skateparks and why?” I think the answer depends on the desired riding features of the skatepark in question. My knowledge of this subject and the terminology is limited.
Fixed wheel unicycle
Lots of people ride regular fixed wheel unicycles in skateparks to great success. There is some riding on ramps including dropping in but by definition there’s a lot of pedaling and gravity is not being taken advantage of. Grinds are executed on rails and boxes and tricks like spins and flips are executed on flat, banks, into and out of grinds, and pretty much everywhere.
BC wheel
I would guess that far fewer people ride BC wheels than unicycles and even among that smaller group even fewer people ride BC wheels in skateparks. The only person I know of is Nicolas Potier. His video includes riding in quarter and half pipes, riding splines, stalling on the lip, dropping in, offroad jumping, grinding rails and lips, riding in a bowl, and lots of other activities. This type of riding takes advantage of gravity but requires a huge amount of skill and control. The BC wheel plates provide a nice steady base but are the only thing you can balance on.
Freewheel unicycle
Not very many people ride freewheel unicycles at this time and I am probably their largest champion. I have not taken my freewheels in a skatepark yet but have a sense of how they might work. You can take advantage of gravity and have a higher balance point than a BC wheel (the seat) but the base isn’t as stable. You would also be able to pedal between obstacles and both increase (by pedaling) and decrease (with a brake) your speed. Some preliminary work with rolling hops and small jumps shows there’s a tendency for my feet to drift off the pedals when I’m in the air but that may be fixed with better technique and more practice.
Unbike
The unbike is basically the front end of a BMX bike. I haven’t seen this used in a skatepark but there’s no reason it couldn’t be. The handlebars provide a higher balance point and there’s a somewhat stable base. It’s not as stable as a BC wheel with plates below the axle. You can take advantage of gravity.
Pegged unicycle
The pegged unicycle (is there a better term for this?) is a variation of the unbike. I haven’t seen this used in a skatepark either but there’s no reason it couldn’t be. The seat provides a higher balance point and there’s a somewhat stable base. It’s not as stable as a BC wheel with plates below the axle. You can take advantage of gravity. Forum member showed an example of this based around a regular unicycle but you could probably build one out of the front end of a peg drift trike and even get a nice disc brake.
Unicycle with drop plates
This is my theoretical variation of the pegged unicycle. Has anyone built one of these? Is there a better name? Instead of putting a unicycle frame and seat on a BMX wheel with pegs you use a BMX wheel with BC wheel style drop plates. This might be the most stable configuration you can use and still take advantage of gravity. Compared to a freewheel unicycle you lose the ability to increase speed easily (although you could push with your leg like a skateboard and BC wheel) and also lose the balance adjustment that pedaling can provide. If you’re getting a lot of air, however, I think it would be much easier to find the plates than the pedals of a freewheel unicycle. My guess is that this is the best configuration for vertical-style skatepark riding. You could probably build one out of the front end of a peg drift trike by adding BC plates and even get a nice disc brake.
Could open up more variety in tricks if you did it though!