I have acquired a grease spot on my dash, apparently from a friend setting his wrapped hamburger on it for a few seconds before I started yelling at him... now it won't wash off - tried dawn dish detergent and back-to-black.
Any more ideas? Or should I just go ahead and shoot him now...

 

Shoot 1st...ask ?'s later!! Have you tride a 50/50 Solution of Simple Green and Water?? Then some 303 or Nero should get your Dash looking good as new!!

 

Black Wow maybe?

With the pervasive nature of fast food grease one can see why it is so bad for you.

 

I'd try to put a few folded over (good) paper towels weighted over the area for a few days to try and 'soak' the oil .... then do what others have suggested

as well as SMACKING him

for treatment I'd use 303 or Zymol vinyl treatment

 

Magic Eraser.