If we're judging best by ones that we kept to listen to over and over (and that's usually how I judge them) there would be two :
Printcrime by Cory Doctorow
One Million Years B.F.E. by Merrie Haskell
Honorable mention goes to "Nightshift in the Automart" by Andrew Gudgel, I listened to it twice.
However, that omits the various and sundry Eekhout story grenades that I have greatly enjoyed, but figured I didn't need to enjoy more than once. I mentioned elsewhere that "Airedale" was the first Escape Pod I ever heard and I new I was onto something good when I did. I also quite liked "Pennywhistle".
A lot of the flash turned on a flash of something new, and once the newness is uncovered, didn't really stand up to repeat listenings for me.
OTOH, I think a great many of our flash contest contestants who took a stab at humor for their flash could stand to listen to "One Million Years B.F.E." because it's hilarious and the funny is really well-done (and I know I'm not even getting all the anthro jokes).