An athame is a magical knife used by Wiccans in ceremonies and rituals. It can be hand-crafted or purchased, and is used for casting a circle, among other things.
Many Pagans today opt to make their own athames. Depending on how skilled you are with metalworking, this can be either a simple project or a complex one. There are a number of websites that offer instructions on how to make an athame, and they tend to vary in skill level. Tips for Making Your Own Athame