Your own 3D parametric modeler
Tiivad 3D
Wings 3D is an advanced subdivision modeler that is both powerful and easy to use.
Godot
Godot provides a huge set of common tools, so you can just focus on making your game without reinventing the wheel.
Blender
Blender is the free and open source 3D creation suite. It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing and motion tracking, video editing and 2D animation pipeline.