Breasts and possibly other anatomical bits are given oddly great attention to their jigglyness, regardless if this is actually simulated physics or part of predesigned animation.
Alternate names: Breast physics
Name variations: boob physics
The first video game about Jiggle physics was released in 1994.
This can include even buttocks, though those are so far quite rarely included.
A product of jiggling bones in skeletal animation which were "intended" for bobbing hair and such.
A montage of several games with jiggle physics in one form or another: