Kendō (剣道 lit. "the way of the sword") is a Japanese martial art/sport based on traditional sword styles. Unlike other sword-based martial arts kendō emphasizes sparring with opponents using bamboo swords called shinai. Kendō is fought one-on-one as a duel and is a very rigorous workout both physically and mentally!
I've also had the opportunity to teach kendō to children at the Boston Junior Kendo dojo in Burlington MA. Though this is no longer happening I hope to start something else up soon.