I think this advertisement from Dulcolax is extremely clever and funny. It's extremely minimalistic in its execution with only the cork lying on the floor and the dulcolax pack in the bottom right.

It's a great analogy of cork=constipation. And the fact that the cork is lying on the floor means the bottle is open, liquid is flowing, etc....Now, not many people like the liquid flowing when it comes to defacating, but if they were badly constipated, it would be a welcome change.

Overall, the simplicity and analogy of this advertisement is genius. Very well done.