10. Doctor Strange
One of the most intriguing rumours that emerged over the festive period was that Benedict Cumberbatch's first duties as Dr. Strange will be to cameo in Age of Ultron, based almost entirely on the timing of Marvel's casting announcement, and the reshoots that were organised for this month. A case of two plus two equals Strange. But it's not too much of a stretch at all, even if the assumption that he won't be super-powered seems to have been disproven by the fact that he was already a known target for HYDRA in Captain America: The Winter Soldier. Why He'll Appear Following on from Marvel's tendency to foreshadow upcoming properties, this makes further sense because of the fairly dramatic shift in tone into Phase 3 for the introduction of the cosmic side of the MCU. Marvel wouldn't want to go in too cold, and having Strange appear as some sort of consultant (possibly post-credits) to confirm that the Twins' powers are Infinity Stone related would fit that agenda. He's also a far easier prospect to shoe-horn in than Scott Lang, who has to wait until he's "discovered" at the start of his own movie to matter in the MCU (not to mention the fact that he's presumably in San Francisco and not New York or Sokovia), or Hank Pym (who has been dismissed as the created of Ultron - though that might be misdirection).