Answer:
1.) RayWilliamJohnson
2.) nigahiga
3.) smosh
4.) machinima
5.) ShaneDawsonTV
6.) Fred
7.) freddiew
8.) collegehumor
9.) realannoyingorange
10.) MysteryGuitarMan
(Note: It might have changed by the time you read this...but I wrote this in September 2011)