This official pin flag from the 2012 Ryder Cup at Medinah is autographed by the victorious European Team. Dubbed the "Miracle at Medinah" (or Meltdown at Medinah if you're a fan of Team USA), the European Team staged a dramatic Sunday comeback to win the Ryder Cup 14 1/2 to 13 1/2. This flag is signed by Captain Olazabal and his team including Rory McIlroy, Sergio Garcia, and Ian Poulter. The only player that has not signed this flag is Peter Hanson. 

Here is a complete list of autographs:

Jose Maria Olazabal (Captain)
Rory McIlroy
Justin Rose
Graeme McDowell
Paul Lawrie
Luke Donald
Sergio Garcia
Francesco Molinari
Lee Westwood
Martin Kaymer
Nicolas Colsaerts
Ian Poulter