Vision
Vision (Paul Bettany) is another relatively new character – at least in his new form of a physical being with extreme superpowers. Having been created as such during the course of events in Avengers: Age Of Ultron, he saved the day and entertained, with his amusing attempts at out-styling Thor. He is incredibly powerful, though, and his allegiance during Captain America: Civil War will undoubtedly be crucial.
We would probably anticipate Vision being loyal to Iron Man, because he essentially created him and because we would expect a being manifested from artificial intelligence to take a logical approach to conflict. Many thousands of innocent lives have been demonstrably lost due to superhero interventions, so the logical response is to implement authority and oversight. There are two factors in the Captain America: Civil War trailers, however, that suggest the position of Vision might not be so straight forward.
There is a brief glimpse of Vision and Scarlet Witch in apparent conflict – in much the same way as we see Black Widow and Hawkeye fighting. Scarlet Witch is evidently using her powers on Vision in a hostile fashion, and we know that Scarlet Witch is – at one point, at least – fighting alongside Captain America, against Iron Man. This would support the idea that Vision is loyal to Iron Man, but Vision seems to be absent from the main preview footage that depicts the opposing factions of superheroes charging aggressively at one another. Will he switch sides, or abstain from the debate entirely? It remains to be seen.