Drumz is the most played Dead song. Between 66-95, they played it over 1400 times.
Besides Drumz though (which really wasn't a "song" per se in the classical sense), the most played song was Me & My Uncle, played a whopping 613 times. Here's the "top 6" (minus Drumz) as it were:
613 - Me & My Uncle
596 - Sugar Magnolia
586 - The Other One
581 - Playin' In The Band
552 - China Cat Sunflower
549 - I Know You Rider
I'm amazed that Bobby could sing M&MU that many times. I mean it's a good song and all, but after two or three hundred, I don't know how he did it.
Oh yeah, I forgot to add--this is all straight from the bible, DeadBase X.
"Now get back to the stands before I shave off half your mustache and shove it up your left nostril. "
Bad News Bears