Richard the Lionheart (1189-1199) is one of England's most beloved kings. It helps that he spent less than a year, total, of his reign actually in England.
The nickname comes from a story that he was attacked by a lion. But when the lion opened its jaws to bite him, he reached into its mouth and down its throat, grabbed its heart, and pulled it right out. This seems wildly unlikely.
He was actually the third son (out of five) of Henry II of England and Eleanor of Aquitaine and not originally intended to be king. Eleanor had been divorced by Louis VII of France for not producing sons, so the fact that she immediately started cranking them out with Henry showed it wasn't her fault.
The oldest son (William) died young, but Prince Henry, his father's favorite, was supposed to be king of England after him. Richard, Eleanor's favorite, was supposed to become duke of Aquitaine, succeeding his mother in that office, and take over his father's French lands--Henry II held Normandy, as had all English kings since the Norman Conquest, and also had Anjou (the county next to Normandy) from his mother. So Richard spent his youth in France, not England, and in his teens led rebellions against his father.
Young Prince Henry, the favorite, died before their father, so Richard became the heir to the throne. Their father died, at the castle of Chinon (in France, illustrated below), just as the Third Crusade was getting underway. Richard raced off to fight the infidel, delighted not to be burdened with anything as tedious as governing. The fourth brother, Geoffrey, had also predeceased their father--killed accidentally in a tournament--so the fifth brother, John, was left in charge of England.
Richard had a great time on Crusade, earning the admiration of Saladin, but on the way home through the Holy Roman Empire he was captured and held for ransom. John had to raise the money to free him, an enormous amount, a "king's ransom," which did not help his reputation with the people from whom money was extracted. (Between the fact that Prince Geoffrey's little son Arthur mysteriously disappeared while visiting his Uncle John, and the excesses that later led to the Magna Carta, John has never had a good reputation.)
Once freed, Richard stopped by the house long enough to be the "good king" of the Robin Hood stories, but he quickly zipped off to France. Although he'd survived Crusade, he was shot down while besieging a castle--where it's possible great treasure was hidden. Dying, he tried to make it to the castle of Chinon, to die where his father had, but only made it into the lower town below Chinon before expiring. He was buried at the French monastery of Fontevraud--the image from his tomb is below.
By the way, you'll sometimes see the suggestion that Richard was gay. This is based only on an account that he and young Philip II of France became very close friends--when not at war with each other. Medieval men, unlike modern American men, found such closeness normal, not a sign of anything queer. In fact Richard, who was indeed married but left no heirs, seems to have been uninterested in sex with anyone--why have sex when you could be out fighting instead?