Definitely leave your room, as the others have said. Exercise does often help, if you're the type who often doesn't get enough to begin with.
See a movie in the theater. Go to the local fruit market. Window-shop a favorite store. It's funny how sometimes I can be feeling a bit down and some brief random encounter with a stranger while I'm out makes me feel better. And this from someone who's also not very social.
If you really don't want to (or can't) leave the house/room much, watch a lot of stand up comedy. I find playing games good for suppressing/ignoring emotion, but it doesn't really make me "feel better." So try something else. Comedy shows etc., (sustained laughter helps a lot), building something with your hands, writing a short story, cleaning/re-arranging the furniture/stuff in your room, whatever you can think of that's a bit outside your normal routine but might give you a small sense of achievement.
And if all else fails, there's always The Shawshank Redemption.
