Well, MacGyver fills me with nostalgia...so does Star Trek...but they aren't necessarily my favorites.
I like Supernatural's S5 Title Card, but that's not a sequence...so, I'll say:
The Title Sequence in Changing Channels
Because the first time I watched it, I was laughing so hard that I couldn't even hear the words.
On an unrelated note: Does anyone know why you can't paste text in the "rich text" window when using Google Chrome to blog? I've managed to work around it so far, but I'm wondering if it's some sort of setting that I can change, if it's genuinely a flaw with the browser, or if it's a unique problem to my computer.