PILGWAY released 3D-Coat 3.5 with an auto-retopology feature with user defined guides for accurate edge loops in Re-topology, Multi-resolution for voxels, Multithreaded merge and nice models preview and more! Check out the 3D-Coat 3.5 features page for a full rundown on this releases many features and improvements.
3D-Coat is a low-cost but powerful sculpting applaiction for windows, linux and mac os, with some interesting features that include Voxel sculpting, Per pixel painting, Improved retopology tools, Improved UV-mapping tools. If you are not familiar with 3D-Coat, take a look at the previous version’s features: