Well, Trying to diffuse the situation verbally is always Ideal, but more often than not, it doesn't work. (at least it doesn't work often for me, people can be so thick headed.) Personally, I always found kicks to the knees and groin to be very effective. Also Elbows to the face and temples, and Knees to the Groin, and Lower Abdomen if you're in close. Depending on the amount of danger, I might also choose to use an eye strike/gouge or a strike (Possibly a Nukite or Shuto) to the Neck/Throat.. I would under no circumstances headbutt a wall. I figure if I'm going to headbutt something I might as well headbutt my attacker, I might get lucky and they'll have a glass jaw. Then again, this is my personal choice of what would be most effective.