Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Material Maker - Cross-platform, procedural texture generation tool.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Substance Designer - Substance Designer is a node-based non-destructive application for material authoring.
ZBrush - ZBrush is a digital sculpting and painting software solution.
TextureLab - Free, Cross-Platform, GPU-Accelerated Procedural Texture Generator.