William the Conqueror
One of the more capable Medieval rulers, William obtained his own kingdom the hard way, he conquered it. Williams conquest of England in 1066 was only one of his many political and military accomplishments. Born in 1027, there has long been a dispute among historians as to whether his mother was Arletta, the tanners daughter, or someone else. His father, Duke Robert ("the Devil") of Normandy, acknowledged William as his son. In any event, William was often called (behind his back), "William the Bastard." While William was acknowledged as his fathers heir, there was still a war of succession when Duke Robert died while on pilgrimage to Jerusalem in 1034. With the aid of king Henry I of France, William managed to defeat his local rivals in 1047, when the young duke was only 20 years old. William then assisted Henry I in disciplining other French barons. But William had grander ambitions than simply serving his king. Williams cousin was king Edward the Confessor of England, and William used his considerable political and diplomatic skills to get Edward to appoint him the heir to the English throne in 1051. He further strengthened his claim by marrying, in 1053, Matilda of Flanders, a descendent of an earlier English king (Alfred the Great.) When the French king got wind of these moves, and their implications, he promptly went to war with Normandy. But William was able to defeat these attempts in 1054 and 1058, adding to his military stature in the process. In 1062, he added to his reputation by conquering the adjacent province of Maine when it's ruler died. The French king was not pleased, but he was reluctant to tangle with William again.
When Edward the Confessor died in early 1066, Harold, the Earl of Wessex, declared that Edward had appointed him the heir to the throne. Undaunted, William quickly gained the diplomatic support of the pope and the Holy Roman Emperor. This made it easier for WIlliam to keep the French king quiet, and to raise a mercenary army with which to invade England, defeat Harold and make good his claim. This William did. But defeating Harold and getting himself crowned was only the first step in taking control of England. The native Saxon nobility had to be defeated and replaced with Norman lords. By 1071, William had destroyed Saxon power, put down some rebellious Normans, defeated a Danish invasion, invaded Scotland and got the Scots to agree to keep quiet and pay him tribute, and gone back to France to re-conquer Maine (which had rebelled in his absence.) He spent the rest of his life, until his death in 1087, organizing the English government. He created a centralized feudal government, something unique in Europe at the time. William was able to do this because he not only conquered the country outright, but replaced the nobility with his own men. Moreover, he made sure there were fewer nobles per capita than in any other nation. The English nobles would eventually rebel, and would do so several times over the next few centuries. But because the royal government was stronger, and the nobility smaller, than was normally the case in Europe, the central government survived these situations in better shape than any other nation.
William didn't exactly die peacefull in bed. He had a bad riding accident and never recovered. What he left behind was a kingdom, and a line of soverigns, that still exists.