Love firefly. Even Serenity was good, though it understandably had to try and appeal to people who may not have watched the show. I had a ripped copy of the entire season. I even printed out DVD cases and stuff for it haha. Just found them and made another copy of those same DVDs while setting up my Plex server.
Edit: Freaks and Geeks was really enjoyable since you see a bunch of big names before they got really popular. Much like Wet Hot American Summer.