People have thought of criticals for a long time when considering weaponry and I would like to point out one thing that everyone seems to overlook.
We shall assume 2-15 everyone agrees is a 1x hit, but for the following I am assuming you have Improved critical in the appropriate type.
With a Rapier/Scimitar you get a 2x, 2x, 2x, 2x, 2x, 2x on 15-20 which equals 12.
A heavy/light Pick you get a 1x, 1x, 1x, 1x, 4x, 4x on 15-20 which equals 12.
A long sword/great sword you get a 1x, 1x, 2x, 2x, 2x, 2x which equals 10.
A Greataxe you will get a 1x, 1x, 1x, 1x, 3x, 3x which equals 10.
I never understood why people don't appreciate picks, particularly at lower levels. Heavy picks are about the equivalent of Vorpals at lower levels.