Underrated Actors/Actresses

New topic of discussion: underrated actors and/or actresses. We can also throw in there underused. The first one I'm throwing out there is Paul Giamatti. For ever since I can remember seeing him in something, I've always thought of him as a fantastic actor. He has the acting chops for quite a lot, but I mostly find him excellent in dramatic roles. This being said, I don't think he is praised highly enough, I don't think he is used for enough roles, and I don't think he is always cast properly in some of the roles that he has played in the past. One of my favorite roles I've seen him in is the HBO miniseries John Adams, in which he of course plays John Adams himself. He does a superb job from beginning to end. I have in fact rewatched that series a couple of times, having it on DVD, just because I can't get enough of him in that series. I tend to get excited about any role he plays, even if the movie is not quite tracking the best, just because I know that with whatever role he is given he is going to do an amazing job with it.

What about you guys? Are there any actors and/or actresses that come to mind when it comes to being underrated and/or underused?