Best ever Dave Gilmour - On An Island in 2006 at the Royal Albert Hall. Never see the like again, now Rick's gone.
Pretty close second Leonard Cohen at the O2 twice last year
Pink Floyd at Wembley in, I think, 1990 and the Rolling Stones later the same summer
I saw Elton John with just Ray Cooper, the percussionist, sometime in the late 1970's and that was brilliant. Finsbury Park Astoria, if I remember correctly
I saw Eric Clapton at Hammersmith in about 1978, Muddy Waters opened the show, limped on, sat on a stool and blew the place away. Slowhand was pale by comparison.
And there's a band about now called Never The Bride who I've seen twice at the 100 Club in London. Two women with a superb rhythm section and just brilliant voices.
And if you like acoustic music, go and see Roy Harper.
But I suspect I'm a bit older than you, and most of your respondents.