thegladiators From any canon, including movie-verse; Iron Man, Thor, The Hulk, Hawkeye, Black Widow. My Cap is post-Civil War, but if you're not familiar with the comics, that's totally fine, since it would all be news to your character anyway. In fact, I think it would be pretty interesting to play comic!Cap against any of movieverse!Avengers, because in his world, they've known each forever, but in their world, they've only just met. Some of them also have very different relationships/elaborate histories, which would create some conflict/confusion. I'd especially love a Tony (platonic or otherwise) from any canon, just because he's such a key figure in Steve's life.
I'd also love to see: Spider-Man (any canon), Sharon Carter, Winter Soldier, Falcon, Wasp, Ant-Man and Wolverine.