Athame

The Athame is a black handled, straight, two-edged knife that represents the element of air and / or fire and is used commanding of spirits, and, most aptly, making symbolic divisions, the most common of which is the casting of a circle, a cutting out of sacred inner-space in which to work.

As the Atheme is not generally used to cut physical materials, the decision of whether or not the blade should be sharpened is up to the user.

Katana as ritual sword

A friend of mine posted this info on using a Katana as a ritual sword. Reprinted here with permission.

Since the katana has been mentioned of late I thought I'd mention
how it is usually used as a ritual
sword as opposed to the usual double edged European sword. With
the katana any projecting energy
is done thru the blade edge,receiving energy is done thru the back
side of the sword. The same applies
to the 2nd sword,the smaller wakizashi as well as the 3rd blade the
long knife known as the tanto.
  Since many of the Japanese swords sold today are mostly
decorative and the handle being plastic some
have argued that spiritual energy won't move along the handle
properly but that is often a matter of the
user's personal beliefs about plastic,most of which is oil based and
that means it contains carbon which
will conduct spiritual energy,but even if you still have issues about
plastic handles,your energy can jump
from your hand to the steel of the blade within the handle and thru
to the tip or from the tip back to
your hand,depending on if you're projecting or recieving energy.