Pinball Havok
Second Life | (2)
For me, the main benefit of Havok4 is that sculpted prims are solid instead of being confined by awkward bounding boxes - no long needing invisiprims underneath sculpted objects saves prims, makes them more realistic, and may lead to their wider use.
But then, I'm not a scripter, so I leave it to this video to give a hint of what Havok can do in creative and capable hands:
[youtube=http://youtube.com/watch?v=wkt2T68QaLQ]