I don't get Logo, but saw the listings and was "WTF?" Then I figured it must be some sort of "Best" list, in order of rank, because in order of the show, it'd be very confusing.
My all-time favorite ep. is "The Body," and is, IMO, one of the best episodes of any show ever shown on TV. Some of this comes from my own personal experiences, but it captured the horror and banality of the death of a loved one like nothing I've ever seen. I think my faves are in line with a lot of others here, "The Prom," "Becoming I & II," etc.
One of the things I enjoyed about BtVS was that even in realy bad episodes, there'd be some redeeming scene or feature. My fave of this is in "Bad Eggs," at the end when Buffy & Angel are in the cemetary the camera pans across to a headstone that reads, "In loving memory." The next episode Angel loses his soul. I've interpreted the camera pan as a bit of foreshadowing to the death of the B/A relationship. It certainly was never the same.
And how much do I love it that even after all these years, we can still discuss fave episodes? Lots and lots and lots, that's how much.