Judo - I love this for the fact that it really isn't offensive. Wrestling and Throwing, there's really not much more to it. No punches, no kicks, nothing. You learn to anticipate and utilize force and balance and even for someone as out of shape as me, it can still be a pretty effective way of discouraging the more violently inclined.
Budo Taijutsu. The art of such can even be practiced slow, (like how there's kumite to Karateka <Karate practitioner), then progress in speed, combos and fluency to enhance reactions and counter reactions, fluency of combos, etc. Pace is imperative for beginners.