A selection of athamés
After study and experimentation, I'm pretty sure that the athamé owes more to high ceremonial magick than any pre-Gardnerian witchcraft tradition and probably is closer to a ritual sword than anything else. But sometimes the best symbol for a thing is the thing itself. I've experimented with something based on a Roman gladius, but really don't like the feel.
At the moment I'm looking for a custom blade something like a cross between a gladuius and an Arkansas toothpick. It should be straight, double bladed, black handle, with a reversed crescent for the guard. The blade itself must be thirteen inches long. That would make it illegal in many states (check legal stuff).
Still, for most purposes, a blessed pocket knife will do as well.