Here is a fun one.
Create a box.
Set it physical
Select and Edit and move it about half way into the ground.
Hold down shift and drag copy side ways.
Stand back and watch the box launch out of the ground.
This only works with boxes other prim types do not.
Boxes seem to have some odd collisions problems with land in general. like the land only collides with the corners of the box and not face.
Goto the Morris Sand box and find the small hill in the center.
Create a a boc 10x10x0.1
drop the physical box right over the hill. the Hill will poke right thru the center of it.