My best show was when I lived in Bristol in the UK for a few years ago and was fortunate enough to go to a benefit gig for the '04 boxing day tsunami.
it was Massive Attack & Portishead playing on the same lineup for the first time ever in their hometown, Portishead's first live show in about 5 years and the support act was Robert Plant from Led Zep. such an amazing evening!
a close second was in November of last year. flew to Melbourne from NZ to see Radiohead play and when i arrived i found out that The Refused were playing the night before. the gig was sold out already but i managed to score a ticket from someone a couple of hours beforehand. i think i was more stoked with The Refused than Radiohead 'cos i never thought i'd get the chance to see them live!