If I were to list my favorite Let's Players… well… I have a lot of them, but in rough order…
ClementJ642
BrainScratch Commentaries
Hellfire Commentaries
The Runaway Guys
NintendoCapriSun
Chuggaaconroy
ProtonJonSA
pokecapn
medibot
The StrawhatNO
The Dark Id
newfiebangaa
wiiriketopray
BikdipOnABus
sshpokc
Keep in mind that these are the Let's Players that I find myself coming back to watch again and again whenever the mood strikes me, and I often find myself waiting for their next videos. I didn't bother to list LP'ers that I don't bother to watch very often, or that I didn't use to watch when I was a bit younger. (For instance, raocaw is an honorable mention that I've seen a few videos of, but I don't actually follow all that closely.) I know slowbeef, Diabetus, Deceased Crab, Chip Cheezum, etc. are big names in Let's Plays, but I've never really gotten into their LP's, so they're not even on the list. Also, as much as I love BrainScratchCommentaries and Hellfire Commentaries, I don't really follow their individual members. (I probably would follow NTom64 and FTA, but they don't have individual YouTube channels that I know of.) As for PCULL and SuperJeenius, I've only paid attention to them so far in collabs with ProtonJon.
So, anyways, on to the meat of the show. What Let's Players do you find yourselves coming back to watch again and again?