Falafel is middle-eastern dish consisting of fried (or baked) balls of chick peas and other spices. One popular method of serving falafel in San Francisco is to make a falafel wrap with vegetables and tahini (or yogurt).
At one point the FBI thought it would be a good idea to track terrorists in San Francisco by monitoring falafel sales. I am not making this up.
Some popular Falafel joints: