Blender
blender.org
Free, open-source 3D creation suite for modeling, sculpting, animation and rendering. It's not CAD (no precise parametric history), but it's unmatched for organic shapes, figurines and artistic models, and its 3D Print…
Meshmixer
apps.autodesk.com
Autodesk's free tool for editing and repairing STL meshes: sculpting, hollowing, cutting, combining models and generating tree supports. Autodesk stopped developing Meshmixer around 2021 and folded some of its features…