I would use a Jō staff ( http://en.wikipedia.org/wiki/Jo_(weapon) ) for it's versatility. In combat, you can use sword, spear and long staff techniques all mixed up, can cause some serious confusion in opponents! On top of that, hardened wood like white oak is a lot harder to cut with a sword than you would think. I've seen my sensei block (not parry, actually block) a katana strike with a quality Jō.
I also don't think I'd be comfortable with a sharp weapon, the idea of slicing through (or into) a human being doesn't sit too well, bashing his brains in seems easier on the stomach somehow.