Far too many best gigs but key ones would be:
Anna von Hausswolff - Any one of the 5 times I've seen her.
The first time I saw Goat, at Supersonic Festival, such a buzz about their performance and they totally delivered.
Dio, back on the Dream Evil tour. Had drum solos, guitar solos, audience participation stuff, a giant mechanical spider coming down from the lighting rig, lasers. It was everything a metal gig should be.
But the stand out band for me would be The Wonder Stuff. I've seen them 60 or 70 times (I've seen other bands more) and they've never done a bad gig, IMHO, I've left every show wanting more.
Worst gigs:
Goat, in Bristol, on the Requiem tour. They took an hour to take the stage after all the gear swap had been done. Then just seemed to go through the motions. I know they're a collective of musicians, so I guess it all depends on who is in the band at the time.
Radiohead, Cov Poly, they were supporting Kingmaker and were dreadfully dull and up their own derrières.
The Fall in TJs Newport. I'm not a fan of Mark E Smith, and this just cemented my opinions of him...