10. Messi vs Manchester United (2009)
http://youtu.be/Pe15uHGeKVU It may not be the most eye-catching, spectacular goal Messi has ever scored, but it was easily one of the most important. Pep Guardiola's side had made it to the Champions League final, against Manchester United in Rome, and were just one win from greatness. Samuel Eto'o's first-half goal put them 1-0 up, before Messi met Xavi's pinpoint cross with a superb header past Edwin van der Sar. It sealed a 2-0 victory for the Catalan giants, and Messi had further enhanced his reputation as the world's best player in the process.