from http://www.jamesaltucher.com/2014/08/ok-one-quote-from-robin-williams/, watch standup before giving a speech.
Louis CK (for the observational humor), Andy Samberg’s Harvard speech (for aburdist), Amy Schumer, Marina Franklin (they are great at connecting with the audience), and Bo Burnham (totally aburdist), JImmy Fallon (for his energy).
and also of course Robin Williams in the 70s (which I have never watched).
I only learned yesterday that although almost all sitcoms are shot using three cameras, they actually hired a fourth camera to just follow Robin Williams around to capture all of his improvised moments.
Then they would leave entire blank pages in the script for Robin Williams so he could do his improvising.