Marvel released a featurette called "In Good Company", in which the company congratulates itself for putting three whole women in Captain America: Civil War. Amongst that, though, we did get a great look at Sharon Carter in action. There's actually a fair bit of new stuff in this featurette. From Black Widow, we have her and Steve talking in church after a funeral — which was one of the first scenes filmed for this movie. A :25 we have Tony saying to her "I'm sorry, did I just mishear you or did you agree with me?" She responds, as we all would, "Oh, I want to take it back."
We see Scarlet Witch use her powers and get, at around the :40 mark, a clearer look at her bringing Vision to his knees, which has been in the trailers.
But the real revelation in this featurette is all the footage we get of Agent 13, AKA Sharon Carter (Emily Van Camp). She had a small role in Winter Soldier, which ended with her joining the CIA. In this footage, we see her at what looks like the Avengers complex from the end of Age of Ultron with Sam Wilson, unlocking some sort of "restricted" file. She also seems to be leading Tony and Natasha to safety:
But the real joy is seeing her take on Bucky, which can't end well but speaks highly of her bravery and skill:
Here's the full video: