I will start with Marcia Gay Harden. She is superb in everything I have ever seen her in. I am watching the Newsroom and was struck by how good of a character actress she is. In that she is an expensive Manhattan lawyer, I've seen her perfect the Texas pageant mom character in Whip It. She plays religious crazy with such believability you'd think she grew up in a cult.
I know it's hard to call someone with an Oscar and a Tony underrated but she really is, if I were casting and needed a woman in her forties/fifities (she also looks damn fine for 54!) for any role, I'd try and cast her.
One last point she has the sexy smirk of a woman who knows she is both attractive and more importantly very smart.
Which character actor or bit part player do you adore?