Etiquette in the Middle East doesn't allow any kind of personal contact in public places. Not even among couples – holding hands, for example, could create a serious problem. Similarly, touching is not recommended in China. Quite the opposite situation can be experienced in Italy, where touching is part of communicating.
A reasonable degree of eye contact is a "must" in most countries. In Japan, however, eye contact is not exactly a part of a communicating, and not looking into your eyes is not rude. Similarly, long looks can be uncomfortable for the other side.
In most places, nose blowing is acceptable only if done quietly, and ideally away from other people. In Japan or China, nose blowing in public places is definitely a faux pas.
Alcoholic beverages somehow belong to holidays and traveling . . . but. While in most of central and eastern Europe a drink is just a part of hospitality, in other places it is not accepted or is explicitly forbidden, such as in Saudi Arabia, Iraq, Iran, Yemen, Brunei, Afganistan, Sudan, Qatar, and also some states in India.
Right hand versus left hand
In Arab culture, the left hand is considered unclean (reserved for bathroom use), therefore it is not polite to use the left hand for anything else (especially not for eating)
Touching someone‘s head is taboo in Thailand, where it is very impolite to touch an adult’s head since this is a form of contact that is reserved for children.
More than a faux pas, it is a pretty expensive to chew or even import chewing gum into Singapore, and far worse to throw chewing gum on the street. The city banned chewing gum in 2004 and imposed a penalty of one year in jail and a $5,500 fine.