I hardly ever wear "message" T-shirts any more. Now I just go for plain, unadorned shirts in various muted colors. My favorites from the past, though, were probably my Empire State Games t-shirts from back when I competed in them (cycling) in the early '90's. Also a few other cycling road race t-shirts and some speedskating meet t-shirts from the same era. I don't have any rocketry-oriented t-shirts (yet).
MarkII