I found metafilter, IIRC via a Sasha Frere Jones review on his blog. My wife was reading his blog a lot a few years back, and one night she sent me to a discussion thread on MeFi that he'd apparently linked to. I've no idea what the original thread I visited was, but do I remember clearly thinking (I swear): "Holy shit! Reasoned intelligent conversation IS possible on the web!"
It became one of my regular stops, and I joined shortly thereafter.
Fondest MeFi memory is the gentling of Godwin's law.
I guess the first time I really fell in love with MeFi was while reading some insanely long thread discussion that got WAAAY out of hand, Cortex had to step in and clean some shit up and lay the hammer down. This one was a bad one. Like people calling each other nazis and rapists and racists (the holy triumvirate of internet name-calling).
It was the way Cortex did it that blew me away. It was with a firm grace, that explained why the deleted posts had been deleted (they'd taken the OP's original frame, and gone far afield) and how to keep things on a more even keel.
And it worked.
Later on when I got to meet Matt and go to my first MeFi meetup (here in SF) I saw that the MeFites were mostly like this.
I also loved when MeFi outed the Dilbert dude for sockpuppeting about his "genius level IQ". MeFi's behavior, both the management and the community, during that internet shitstorm, stands as a high-water mark to me.
Oh, I also love my moniker "MeFi's own Adam Savage".