This guy probably knew what he was doing

When thinking about fragile items, eggs spring to mind right away. They have an extremely thin shell that will break under very little force. You could drop one from some distance and it will more likely than not break apart. You could push it with force in the wrong direction, and it splits. Tap it lightly on the side of a bowl, and it breaks the shell. Eggs break on purpose; sidway force is met with no resistance, so they're easy to break whenever you're cooking with them.

There are probably other things that are fragile as well, however most times they will take more pressure or a quick impact before disintegrating. Glass probably will break after dropping it, although it normally stands against being touched or tapped before breaking. If you bend or dent a plastic container they will break before snapping. Eggs neither bend or dent. They don't even go through a phase of some kind. They go right to the end point of breaking, then break quickly and completely. It won't take a special type of force or tool, it just simply takes force to go in a specific direction and the shell breaks. Not that complicated.