If your looking for a mechanical application, I like Solidworks. In my opinion Solidworks is more "user-friendly" than products like Autodesk Inventor or ProE. If it's too pricey for your budget, try Alibre...... but it is just my opinion.
Solidworks and Autodesk Inventor seem to be very common.
I agree that Solidworks is best choice for 3D CAD design. Its Solidworks Professional and Solidworks Premium have advanced design and modeling features.