One little tip you find in lists of do's and dont's for visitors to Greece is to avoid making any gestures that involve displaying the palm of the hand, for fear of this being interpreted as the "moutza".
http://en.wikipedia.org/wiki/Moutza
I notice that here in Cyprus drivers generally hold up their hand for a few seconds with the palm pointing outwards very much as British people do in order to thank other drivers for letting them move out onto the main road etc. This surely resembles the moutza, which makes me wonder if this gesture is used or recognised here. I can't say I have ever seen a Greek Cypriot make this gesture as an insult.