Mangaminx, NintendoCapriSun, ProtonJonSA, Chuggaa's ok sometimes but too childish in his humour for my tastes, and some Retsupurae every now and then. Oh and HANKGAMES!! DFTBA!!!
He isn't mainly a let's player, more so an informational channel, but he has videos of Borderlands and Skyrim on his channel. I'm almost certain he's going to post videos on Diablo 3 as well. He's hilarious.
I also never understood all the hype about Chuggaaconroy. He's extremley popular and his videos are excellent quality, but his commentary is bland IMO. Perhpas it's because he's more focused on providing information about the game he's playing instead of making jokes.
People still watch these things? When they got rid of the timelimit the videos they would put out got too long and overdrawn for me. I only watch Retsupurae nowadays.
Back when I watched LPs I'd watch 900RedYoshi(until I figured out how much of a d-bag he was), NintendoCapriSun, Chuggaconroy(not so often though), and SonikDude101. I still watch the latter 3 from time to time.