LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Proteus PCB design - Proteus PCB design combines the schematic capture and ARES PCB layout programs to provide a...
FreeCAD - An open-source parametric 3D modeler
QUCS - Qucs, briefly for Quite Universal Circuit Simulator, is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit.
Sculptris - Sculptris: Enter a world of digital art without barriers.