Armory Paint is a 3D texture painting software written to run entirely on the GPU, and is aimed at PBR texturing.
Ranked in these QuestionsQuestion Ranking
Pro Paint on multiple maps at once
Armory paint allows artists to paint across multiple maps at once. This allows for easy creation of coherent color, roughness, and bump maps.
Pro Node-based brushes
A simple and robust "blender-based" node system to modify brush channels.
Pro Entirely GPU-run
Supports GPU acceleration. Since it is run entirely on the gpu, it makes painting huge maps nice and smooth on modern graphic cards.
It is not completed yet, which may lead to support drop, or a software that is not entirely usable.
Con No projection on normals
The brushes are projected with a simple viewport projection, which can lead to weird warping of the brush on irregular surfaces.