A moment ago I posted the "Agents of S.H.I.E.L.D." pre-tease, which opens with a motion-blurred action shot of an unidentified person(?) rescuing a woman from a burning building by jumping out the window and landing safely with enough force to crater the pavement on impact.
Below the jump, some screencaps of the very brief action-shot for a clearer look and possible guesses as to who this might be:
While allowing that the aforementioned motion blur could be further obscuring things, what this looks like is an unknown woman being rescued by a larger and unusually-powerful unknown man of apparently darker complexion. Is this The Hulk? I don't think so - he's not quite "Hulk Big" and I don't think the current Movieverse Hulk runs on the Silver Age comics mechanics of Hulk changing size depending on his mood like the Ang Lee Hulk did. Also, this guy appears to be wearing shoes, and his hair is either blown-upwards or styled in a manner that doesn't scream "Hulk" to me. My (and I'm betting a lot of other people's) best guess? Assuming for a moment that this is a Marvel character and not someone made up for the series, this could be our first glimpse of a live-action Luke Cage.
A mainstay of Marvel's aggressive (if occasionally awkward) diversity push in the 70s, Cage was a wrongfully-imprisoned black youth who was subjected to experiments in prison (yet another half-formed attempt to recreate the Super Soldier Serum that created Captain America) that wound up making him super-strong and virtually indestructible. You'd think they'd test something designed to that on anyone other than convicts, but there you go. He was mainly popular in the 70s before getting sidelined for a good long while, only to be brought back to the forefront in "Alias" and soon promoted by positive fan response to being a major fixture of the post-Mansion Avengers lineups.
If this is him, it makes a lot of sense: Cage is a street-level guy, doesn't go in for elaborate costumes or gear and his abilities are fairly simple to visualize. He also has (or had) a fun, story-ready gimmick: Cage was New York's resident "Hero For Hire" - instead of going out looking for wrongs to right, he let clients come to him and procure his day-saving services. He'd been previously set to be a recurring character in the "Alias: Jessica Jones" TV series, which never went to air and may or may not have had some of it's assets folded into this project.
Secondary possibility: That the rescuer looks to be of notably darker complexion than the woman could be an illusion of the blur/shooting, in which case that could be anybody. There've been various "official" explanations, for example, as to how Coulson is back; but a popular fan theory going all the way back to "Avengers" has been that the original Coulson is indeed dead and this one is an LMD ("Life Model Decoy," aka "a robot") that will wind up being coverted into The Vision for a future "Avengers" sequel. Some additional tangential "evidence" to that end: Of all the onscreen superheroes, Coulson is most closely associated with Captain America; whose movie featured a hard-to-miss cameo by a certain artificial-man who, in the comics, was used to build Vision's body. It doesn't look like a suped-up Robo-Coulson is making the save here, but it's a possibility sure.