Marvel has absolutely rivers of characters in its portfolio. Some are greats, some have been scenery, but some of the supporting players are really cool, and could use some spotlight. Who would you like to see get a mini-series of their own to see if they got the chops?
I vote Lemar (Battlestar) Hoskins. I'd probably vote for seeing him take up the Nomad name, but everything I've seen of him suggests that he is an underappreciated gem. Best part is, even though his power set is relatively generic, it also allows him to be plugged into a whole lot of different stories.