I've been to quite a few. Used to write a little local rag on the music scene at a very young adult. They span the genres, but most of my stuff focuses on a certain genre as you'll see...so just a few:
7 Seconds, The Descendents, Primus, The Red Hot Chili Peppers(several times), U2, Black Flag, Henry Rollins, Siouxsie and the Banshees, Nine Inch Nails, Meat Beat Manifesto, etc, etc, etc. I'm listing the ones I enjoyed at the time, there were other things I went to that were more dance or rock, but the alternative stuff was the mainstay and what I enjoyed most then.
I've probably met more then I've seen in concert though. It was a fun thing to do before one gets too serious with life and I was lucky enough to do it in a tropical environment(Florida). And I always behaved professionally, so I usually had a good deal more access then just your average kid star-gazing. It was fun.
I hung with an artsie fartsie crowd, many of which are still into that scene.
Kind of fun to reminisce with them that being the case since they are still into it.
Oh, as for most memorable(and disappointing)...a Circle Jerks show where the concert ended about 2 songs in because of the bloody stupid skinheads throwing bottles at one another
and the times we got to sit right off stage and watch the shows. Best...Henry Rollins and the Chili Peppers put on really terrific shows.