10) Alexander Hleb
Arsenal signed Alexander Hleb from Bundesliga club Vfb Stuttgart in 2005 for approximately £12m, but the Belarussian went on to become little more than a nearly man at the Emirates Stadium.
His dazzling skills and carefree manner on the pitch rarely translated into end product and he was largely frustrating for the Gunners, but they did get their money back when selling him to Barcelona.