arm
WYR be stranded on a Ferris Wheel at the top or in a small motor boat in the middle of a lake (no, you don't have oars) for 4 hours until help arrived?
Javelin - because I would have a better shot at not killing someone. Who knows what direction the discus would be going in when I stopped spinning. I'd probably fall down from being dizzy and clunk myself in the head.