Sculptris 1.0

Sculptris is a powerful application for three-dimensional sculpting. This feature-rich application comes with an easy-to-use menu that will grant Mac users quick access to all of the features.

You start the modeling process from a sphere, and perform various virtual sculpting actions on it(crease, draw, grab, inflate, pinch and smooth) to get the desired outcome. For any action, you can modify the area size and/or strength, in order to make deeper or larger modifications.
It is easy to work with this piece of software, since it is highly responsive to commands and runs low on resource consumption. One relevant aspect of using this sculpting program is that every action is symmetrical. However, the symmetry can be turned off if that suits you better, but once done so, you can't revert. Another key feature is that you can import or export objects and projects, in order to create more complex items. The application comes with high applicability because it provides a wide variety of predefined materials for the basic sphere.

Briefly, you should give Sculpris a try; it is free, it comes with high applicability and high functionality, and can be used by beginners and advanced users alike.