The ancestral line I am working on at the moment is the family of Tosny. Their surname has been written a number of ways including Toeni and Tony. They are Norman, however, there is evidence that suggests that they may be descended from an uncle of Rollo the Viking who conquered Normandy in the 10th century.
This family take their name from lands around the French town of Tosny along the Seine, they established themselves at Conches and were the French equivalent of the Bigod's, Earls of Norfolk - they were troublemakers to be precise.
My branch ends in the early years of the 11th century with the death of Godehold de Tosny and begins (in England at least) with Ralph de Tosny who is stated to have been a standard bearer at the Battle of Hastings.