(According to the internet) 12th May 1990. Midnight Oil at Wembley Arena, Blue Sky Mining Tour, there wasn't a bar with staff in the whole of London that night. The raw energy was amazing and we were on the barrier.
Both of the last Eels concerts I've been to were pretty stunning. Managed to see Marillion on the Clutching at Straws Tour when they still had Fish. (I've not really seen anyone small that become big that I cared about.) We saw a well past the prime of their fame Big Country play Bristol town hall (or some such) in the early 90's which was a huge thing for my wife as she'd always been a fan and they still had it, we drove the width of the country for that one.
The first time we saw Green Day (Milton Keynes Bowl, the 20 year old was 10 I believe and it was the first gig they'd ever been to) I now know that they are hugely formulaic in their stage show, but they are comfortably in the arena performer bracket with what they give the audience and before you've worked out the trick it's amazing. Seeing Frank Turner support them at Wembley Stadium was also great, just because you could tell how much it meant to him to be there.
Wheatus at the Forum, Tunbridge Wells in 2011 (or thereabouts). Their schtick is to have no set list and just do songs that are requested from the crowd (again, a great trick because it makes every gig seem spontaneous even though they know the ball park of what is going to be called for and can 'only hear' the ones they've rehearsed) and we called for
Home Town which is an amazing song. Brendan heard the 20yr old, but said they didn't do it live (understandable, it's about the twin towers) see them at the merch stand after as it was the second gig we'd called for it at. The four of us were herded out the back and he played it for us acoustic, Math the Band (one of the supports) appeared at the door to listen. Being a huge Wheatus fan, I'm unlikely to ever top this.
Wish I'd liked The Smiths when they were still together, would have liked to have seen XTC before Andy Partridge succumbed to stage fright (i.e. in the first 20 minutes or so of their career.)