I think we (most of us at least) were just blessed to be part of the Pinacle of Barca because of Messi and company, so just everything Messi was involed in was a blessing... so many matches, moments to point out...
I became a Barca fan as soon as i started to know and love football just because our legend Stoichkov was and will always be part of it... but with Rivaldo's, Ronalndinho's, Xavi's, Iniesta's, Puyol's, etc it kept on growing, so at least I cannot mention a single moment...
But what I would say were the sweatest moments were the ones when we struggled the most and we just needed that spark to turn things around, whether it was someone like Rivaldo, Ronaldinho, Messi, the La Masia boys, it just gives me so much joy that we could crow back from every problem just because we are Barcelona