Fig Sign
An interesting sign with very different meanings is the “fig sign". The thumb is poking out between the index and middle finger. In ancient Rome, it was a sign for good luck and that meaning has survived in Portugal and Brazil. However, in many other countries, as far spread as Indonesia, Turkey, Greece or modern Russia, it is a very rude signal meaning, "screw you".
OK Sign
The thumb and index finger forming a circle with the hand raised, is the universal American sign for "OK" or "I agree" or "excellent". The same sign however has a vulgar meaning in many South American counties, especially Brazil, and may provoke an aggressive reaction. In Spain, it is a sign for cuckold, certainly not appreciated by the person who is the recipient of the signal.
Hand Thrust
In America and many other countries the hand thrust out with the palm held upward and outward is understood as a well-meant warning, in the sense of "stop", or "danger". But if you travel to Greece, beware! If the fingers are splayed, you are in the presence of a sign known as "moutza", which is an extremely offensive and aggressive gesture. Curiously, the signal has the same meaning in Pakistan.