The concert I enjoyed the most was by a Dutch hardcore band (I can't remember their name).
The gig was at a small youth club in front of an audience of no more than 20 people.
After the first song or so I "danced" (pogo, mosh, whatever) for the entire show.
I was impressed with their sound which reminded my of Nirvana's Bleach at times.
Oh, "never seen" haha. Well I didn't see much of the show because I was so into the music.
Anyway, it was great.
Best concert I've never seen. Hmm. I have no idea.