William the Conqueror
Sometimes known as William the Bastard, having been born the illegitimate son of the Duke of Normandy. William inherited the Duchy upon his father's death, but is best known for succesfully leading the Norman conquest of England.
William first attempted to gain England through diplomatic manouveuring. He first claimed that Edward the Confessor had named him successor in 1051, and then in 1064 he convinced Harold Godwinson to swear fealty to him and relinquish his claim to the throne. The latter event almost certainly took place under duress, and the former may not have happened at all, but he used both as a pretext for invasion when the witan declared Harold king in January 1066.
William delayed his assault until late September, waiting for favourable winds. All this stretched Harold's resources, as not only did he need to stay on high military alert for several months, but he also had to fight and defeat Harald Hardrada at the demanding Battle of Stamford Bridge.
William's victory at the Battle of Hastings marked a turning point in English history. Not only was it the most successful invasion of Britain by a foreign force, it also marked the begining of a new dynasty. All kings of England number themselves from the ascension of the Norman kings.
Having been crowned in 1066, William set about securing his new kingdom. Uprisings were brutally quelled, Norman lords were installed into places of power, and by 1072 the whole of England had been united once more.
William's burial was...less than dignified. By the time of his death, he had reached around 300 pounds. Not only was it extremely difficult to put that much flab into a casket, but when the pallbearers attempted to close the casket at the funeral, the noxious gases of death were released from William (to put it lightly), and the entire crowd ran to the nearest garderobe in disgust.