1) FreddieW - What can Insay? Freddie Wong does high-level special effects with an extremely small team. He also teaches people how to do their own stuff.
2) Smosh - For obvious reasons. I've liked Smosh pretty much since day one. Sex Ed Rocks Ft. I Set My Friends on Fire is by far the funniest video Smosh did.
3) PewDiePie - He's the main reason for me to even consider getting Amnesia: Dark Descent. He's got a cool cult following even though he's not very well known.
4) TwoBestFriendsPlay - Same type of thing as PewDiePie but with a larger variety of games and two people instead of one.
5) This one is a toss-up between Dorkly Bits and College Humor. Both are exceptionally funny and quite expansive.