Well, when you get to be old (*ahem*cough*) you just cant narrow it down to absolute favorites. Rather, you end up with a looooong list of "Man, I really like that song" songs.
Over the Rainbow (favorite version by Israel Kamakawiwo'ole)
http://isaraurl.com/OverTheRainbow - click track 14
Cat's in the Cradle by Harry Chapin
Origin of Love from Hedwig and the Angry Inch
Golden Slumbers The Beatles
Crazy Train Randy Rhoads and Ozzie Osbourne
Animal Crackers in my Soup Shirley Temple

Comedians...that's an easy one (or two). All time, I have to go with Mitch Hedberg. Sadly, his life was cut tragically short.

But after Mitch, I'd go with Demetri Martin.

edit: I dont have a favorite Mitch Hedberg album or anything, just all his stuff. Same with Demetri.