Take the biscuit/cake
To take the biscuit or cake means to carry off the honours or the prize, and is sometimes said or used with a touch of surprise or incredulity. It dates from the mid-19th century in America where cakes were often offered as prizes at social gatherings. Take the biscuit is the later British version and dates from the late 19th/early 20th century. Some sources date the origin of taking the cake from as far back as the ancient Greeks but between the Greeks and the first citations in English from the 19th century there is no known record of it, which casts serious doubt on the Ancient Greek origin. See also Piece of cake and cakewalk.