Test geometry provides some built in geometry to prototype and experiment with. Not only does it provide a more interesting starting point than a torus, but it is also more representative of the sort of geometry your effect will have to deal with: multiple components, holes, and not perfect geometry.
A normal pig has forty-four teeth. This pig has none.
Position of the center.
Rotation of the geometry about its center.
Increasing the difficulty adds more problematic issues to the incoming model and brings it closer to the sort of models your tool will likely have to deal with.
Clean mesh with well-sized polygons.
Single watertight mesh with texture maps.
Open meshes with multiple components.