In Citadels, Ann has the crown and Bill chooses the king. The assassin kills the king. Who keeps the crown at the end of the turn?
The crown goes to the player that chose the King role card at the end of the round.
Fantasy Flight Rule book (page 14).
... If you are murdered, you skip your turn like any other character. Nevertheless, after the last player has played his turn, when it becomes known that you had the murdered King’s character card, you take the Crown (as the King’s heir).
The King gets the crown when his character is revealed whether he is alive at that point or not.
Otherwise the king would be exceptionally weak IMHO as whomever had the crown could continually pick the assassin, assassinate the king, keep the crown, and first pick the assassin again. You can argue that they should be assassinating other characters besides the king, but seeing as there are fewer yellow districts than any other color the King needs all the help he can get...