I think the photo below is a powerful image. It's of a supporter of Iranian presidental candidate Hossein Moussavi protecting a riot squad policeman after he was injured in skirmishes with protesters in Tehran. The green shirt is protecting the guy from his own fellow protesters, in other words, from the same people the police officer was probably beating just moments earlier. The green shirt obviously thought this officer had suffered enough and did not want him to be killed. A moving display of humanity. The image will stay with me for a while. I found the photo at Boston.com's Big Picture, which is a great site, btw.
Addendum: I just found this YouTube vid of the same thing happening. Moussavi supporters protecting a member of the riot police. The running commentary is in Italian.