Seeing Ellington for the first time in 1962(?). Art Ensemble, Sun Ra, Albert Ayler, Brass Fantasy, Ornette Coleman, and David Murray on their first UK visits. All absolutely unforgetable. A little more recently John Scofield Quartet with Joe Lovano in 1991(?). I'm probably being unfair but a lot recent things and to some past concerts (and I've been to a lot) but most seem insignificant when compared to these. The sound, the atmosphere, spine tingling.