1. Geek & Sundry (hands down the greatest thing that ever happened to YouTube)
2. nigahiga, HigaTV (one of the best sketch/hybrid comedians ever)
3. Vsauce, Vsauce 2, Vsauce 3 (a perfect blend of history, science, fun-facts, and quirky humor)
4. Numberphile (a fantastic math channel that takes complex mathematical topics and makes it fun to both math literate and illiterate people)
5. The Amazing Atheist (a comical rant channel that discusses stuff like politics, religion, and other social issues from a liberal point of view)
Close runners up: DEATH BATTLE!, MagicofRahat, Khan Acamedy, minutephysics, The Young Turks.