The first AP I listened with Aaron as a player was Room B12. God, that moment when Aaron [spoiler]gave his business card to the serial killer being controlled by the ghouls[/spoiler] I will never forget. But it's been such a great experience listening to him slowly become more and more determined and bad-ass. Like his Dark Sun character, the Eladrin Ranger who actually stood up against Jason and Tom's characters and fought for his (somewhat skewed) sense of justice.
I think Aaron's crowning moment of bad-ass was in the Call of Cthulhu scenario run by Ross, The White Stairs.
"We'd like to borrow it." (the car)
"Well, I'd like to do that but there's a bit of a problem with the bloodstains"
"...What?"
*Punch*
Also, I posted this a while back but it deserves to be mentioned again, as this is how I believe lawful good characters should be played. Not as "goody-two-shoes" but as a person that will always stick to his convictions, no matter the outcome. And I think Aaron showed with his Eladrin Ranger that he can play it this way too.