It's good easy to learn to use for MEP Drawings Brics CAD can use Cad & BIM extension file DWG # Philemon _Dubai
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
progeCAD - progeCAD is DWG/DXF-native CAD software, built for professional drafting.
SketchUp - 3D for Everyone
MicroSurvey Software - MicroSurvey CAD is a full-featured CAD package that lets you do everything from creating point clouds to designing complex survey networks.
FreeCAD - An open-source parametric 3D modeler
Autodesk DWG TrueView - Get a free DWG viewer to view, open, edit, and convert .dwg files, the native file format for AutoCAD files. DWG Trueview includes DWG TrueConvert.