My vote is the Buck Dharma Band T, which happens to be the Silver Anniversary today.
The story of the T, Melne worked up the artwork. I actually saw the T’s being Screen Printed in Virginia Highlands (Atlanta) by Eric Snoddy. Eric was the Band manager of Fuel A.GA, the warm up band for the BDB. A lot of Prid Pro Quo happened, with Eric wanting to record their new album professionally (How lucky was he George Geranios did this for them)!
This picture is actually from my 25 Year old shirt. Nothing has Come Close to holding up that well !
The best concert shirt for ME would be one where I somehow managed to get the whole band to autograph it with the most permanent marker available. And of course with the date and name of the concert (or city) "autographed" on there too, maybe even with something like "Joe, thanks for coming out" thrown in somewhere. That would be one I wouldn't part with.