15. Falcon / Captain America
Sam Wilson made his first appearance in Captain America: The Winter Soldier when he proved himself to be a trusted friend and ally to the Star-Spangled Man. He not only assisted Steve Rogers in the fight against Hydra, he used his mechanical wings to battle the Winter Soldier - unbeknownst to him that the pair would become unlikely friends in the future when Sam took on the mantle of Captain America.
Unlike Steve, Sam didn't take the super soldier serum, so that means his Captain America is more human than his predecessor. He's more vulnerable, yes, but as we've come to expect from the human characters in the MCU, there is nothing "mere" about these mortals. With exquisite combat skills and the aid of both the iconic Cap shield and his trusty wings from his days as The Falcon, Sam is a formidable hero more than worthy of carrying on the legacy of Captain America (and bringing some more humanity to it).
When we first met Sam as The Falcon, he was one of the strongest people in the MCU, and he's only grown since then. Like Hawkeye, he may not have super-powers, but he knows how to handle himself against larger-than-life threats, all while protecting others - it doesn't get more Captain America-like than this.