I take it we're only talking maiden here or else I'd slip "Blazing Away" in from... er... Blaze.
As for Maiden the Breaking in Bruce (Palais Lido, Milan, Italy 30/10/81) mainly cos Remember tomorrow from the show was on my first metal single I bought.
And, at the other end of the scale Rock am Ring 03 either the VCD or CD, cos they, more than anything else, proved the boys could still do it.