12. A.I.M
Like the Rising Tide, A.I.M has a plethora of resources with which Ultron could work and, as the most recently used evil organisation in an Iron Man movie, it's not entirely impossible that they could still be around for the Avengers sequel. Aldrich Killian had big plans for A.I.M - and a keen interest in Tony Stark's work - so to think that he might have been working on something like Ultron, or to think that Ultron might be interested in their work, is surely not out of the question. Ultron is known to utilise drones and soldiers, so perhaps he might want an army of Extremis-powered henchmen? It's unlikely, but don't rule an association with A.I.M out.