As anyone will tell you, it's not the weapon that matters, it's in how you use it that makes all the difference. Knowing how to use a weapon is more important than anything. I personally have a fondness for banshee (or more correctly, the original dha or darb sword types) swords, a blade shaped and functioning something like a giant machette. It has enough length to give it sword status and a shape that is perfectly fit for heavy, supreme cutting power. Only drawbacks are that they are usually made with a wide hilt (handle) to balance with weight of the blade and the hilt further widens towards the base of the blade to form the pretty much nonexistent guard. They also tend to be made with a single handed bias... Depending on the specific design, you'd use it like you would a katana as it serves a similar function (being a curved blade).
As you can see, the thickest part of the blade is centered towards the tip, giving it a great amount of force at that region because of the weight balance. A katana would usually have its center of balance/gravity towards the bottom of the blade (if I remember correctly).
I had the interesting idea of killing someone with a glass with external and internal glass powder and chips, which would be pressed over the mouth of the person, waiting for them to give in and it would be most painful.
However, that would not be quick enough, so I will come up with something else.
Excuse me, but does this smell like chloroform to you?
Always reserve the right to become smarter at a future point in time, for only a fool limits themselves to all they knew in the past. -Alex