Cheetah3D is a lean, fast, and elegant 3D modeling, rendering, and animation package with an easy learning curve. It was written from ground up in Cocoa and offers many powerful tools like subdivision surface modelling, joint based character animation system, morph targets, UV unwrapping, texture painting, PDF import, HDRI, radiosity, renderings, etc.
The possibility to extend Cheetah3D with JavaScripts and support for many common file formats rounds out its feature set.