RenderMan - Advanced Technology from Pixar Animation Studios for Rendering VFX and Animation
Kerkythea - Kerkythea is a freeware software that can produce high quality renders without spending a cent on software licensing.
V-Ray - Learn why V-Ray for 3ds Max’s powerful CPU & GPU renderer is the industry standard for artists & designers in architecture, games, VFX, VR, and more.
LuxCoreRender - LuxCoreRender is a physically based and unbiased rendering engine.
Octane Render - Octane Render is the world's first GPU based, un-biased, physically based renderer.
Sunflow Rendering System - Sunflow is an open-source rendering system for photo-realistic image synthesis