I'm a mechanical engineer and I use Autocad on a daily basis to make 2d drawings. I also make 3d Cad models; Creo Parametric is my preferred software but I can also work with Solidworks and Inventor. In cases where further analysis is needed, I usually use the tools provided in one of the software listed above to perform motion analysis and stress analysis. When the mechanisms I work on are simple, I might use Mathcad to make the calculations myself; Mathcad makes it easier to share calculations with anyone.