Blender

https://github.com/agmmnn/awesome-blender

Addons

• QuadWrap: retopology add-on for Blender that lets you instantly generate retopology over the cylindrical paths of your models

Blender as Hammer

Some interesting posts by passivestar about using Blender as a Valve’s Hammer level editor:

• Making holes in level geometry
• Knife intersect
• Copying material
• Stairs
• Shear operator - easy cornered hallways
• Lowres polyhaven
• Polyhaven + ucupaint

Here is the list of Blender addons they are using:

• omnistep
• quickmenu
• uvProject
• polyhaven
• ucupaint
• Copy Attributes Menu