Shogi
According to ChessVariants.com, "Perhaps the enduring popularity of Shogi can be attributed to its 'drop rule'; it was the first chess variant wherein captured pieces could be returned to the board to be used as one's own. This has the consequence that few games are drawn, which is a weakness of international chess. David Pritchard credits the drop rule to the practice of 16th century mercenaries (ronin) who switched loyalties when captured—no doubt as an alternative to execution".