At the moment I'd say
Cryaotic is my favorite - I really enjoy his commentary and humor. I've watched most of his playthroughs, and his weekly streams on twitch with friends ("
Late Night with Cry and Russ" - I prefer watching the archives though, because they frequently go on for like 8+ hours straight :P).
I recently found Dodger (
PressHeartToContinue)'s channel through Cry's too and I really like her personality and sense of humor, but she doesn't often play games that I want to watch.
And I used to watch a lot of Markiplier, but not so much now as his channel's gone kind of 'PewDiePie' lately (whom I have nothing against and used to watch as well), where he just plays a lot of flash games, and actual gaming series are kinda few and far between. Still, I really liked some of his older series and Drunk Minecraft still cracks me up.
I recall watching him play a bit of Don't Starve. He's funny, but I got a bit bored since he wasn't very good and didn't make much progress (well, I watched his really early playthroughs of it and noticed he's still playing the game, so he's probably gotten a lot better).