Heavy Military Hovercraft 2.0 (crate)

These boats are BIG, but detail is quite good and they're moddable, so they're excellent as the basis for custom builds.
If there's a flaw it's that the instructional notecard is extremely sparse... yet there's a LOT of controls in the pop-up menu that aren't explained. The learning curve is therefor a bit steep, though you can use it as-is fairly simply.
All in all, excellent value for money.