Butter one side of several pieces of bread. Allow them to fall to the floor by pushing off the edge of a desk. Invariably, they fall butter side down! (Well, MOST of the time...) Why? Murphy's Law? [See Murphy's Law or Jelly-Side Down, The Physics Teacher, V26, p392, 1988] It's basically the rotation setup by the uneven weight since one side of the slice is heavier. (Try dropping a hammer without rotation...)