With one exception we have always had great tablemates. The exception was a family, Grandma, Grandpa, daughter and her 5 year old son. Since it was our family, Granny, Grumpa, daughter and 10 yr old granddaughter, we thought at first it would be a perfect match.
My absolute pet peeve in life is unruly children. This 5 year old was permitted to do whatever he wanted to do regardless of the consequences. For two days we sat and watched him play with his food, make a complete and utter mess of the table and fuss and carry on. Fortunately on the third day, a misunderstanding between the waiter and the grandfather caused them to storm out of the dining room and never return. Just how lucky can you get. :-) Other than that one occurance we've dined with either friends, family or people that we found quite charming and interesting.