It's good easy to learn to use for MEP Drawings Brics CAD can use Cad & BIM extension file DWG # Philemon _Dubai
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
FreeCAD - An open-source parametric 3D modeler
SketchUp - 3D for Everyone
Sculptris - Sculptris: Enter a world of digital art without barriers.
meshmixer - meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.