I use Rhino 3D, Its real nice to be able to build stuff virtually before you ever start actually cutting material. Saves on scrap and headaches a lot of times. It is nice to make sure you get all the correct length bolts too and stuff like that
I've used Rhino 3D a lot for designing hovercraft projects, and also some woodworking projects. I'm also planning on doing a lot of designing on my next hot rod project in rhino too, a 40's-50's style truck, but that project is going to be a ways out yet......
I can save A LOT of work on carving a prop by first designing it in in rhino then printing out templates for each layer. Then I already have a rough shape to start carving on instead of a giant square blank.
Here is one of the hovercrafts I designed on the computer. I actually made templates for all the components and made them, and then the hull last, and put it all together and everything fit perfectly.
And here is the hover in real life after we finished it. Its nice for playing around with paint jobs too