The Tau Cross or T-cross continues to be an important symbol in the Catholic Franciscan order. Wearing the symbol is a tradition that goes back at least as far as St. Anthony of the Desert in the 4th century, who had a Tau Cross on his monastic cloak. The Roman cross of execution on which Christ hung was likely to resemble this cross more than the familiar "Latin cross."
The Greek letter Tau ("T") represents the cross and Christ in some very early manuscripts of the New Testament, often conjoined with letter Rho to form the Staurogram.
So the next time someone asks you why you wear the letter T around your neck, you have a conversation starter!