well for the most part I watch a lot of Let's Plays, I see a lot of the big names listed so I'll try to go with some that I don't hear as much about
-GrimithR -one of my favorite LP'ers on YT right now, highly intelligent, funny to listen to, and when he gets mad (or fucksnaps, as he calls it) out and out hilarity can ensue
-ogma001 -another decent LPer
-Paulsoaresjr -ok so he might be pretty well known, but he's my favorite minecraft vidmaker, I learned a lot from his Survive and Thrive series, and he's branched out into a lot of other games as well (also for those who prefer family-friendly videos, his are excellent)
-MarbleHornets, EverymanHYBRID, TribeTwelve -Slenderman, and three of (IMO) the best channels thereof
-EpicMealTime -obvious reasons
MiracleofSound -more obvious reasons
oh and there's this guy who goes by TheSavageOblivi0n...but I dunno...I've heard he's kind of a dick XD