While not a "CAD" software there are very compelling reasons to have this a designers wheelhouse of 3D modeling tools.
- It's free and always will be, runs on a Mac or PC, and has a very strong community of users and developers. - Offers a wide range of different tools such as 2D sketching - Grease Pencil, as well as sculptural tools aka zBrush, and an amazing rendering and animation suite. - Customization allows users to really get in to the software however they so choose. Being able to create code/scripts or purchase ones that suit ones needs from the market place also adds a level of most other packages don't.