Glee has been one of my favorite shows since the very beginning (I still can't believe I couldn't pay attention to the pilot when it originally aired because I was writing my final paper for a Russian Politics class--I got an A), and while it has gone a bit downhill since a lot of the originals graduated at the end of season 3, it is still a pretty fun show (except when it gets serious with episodes like Shooting Star).
This scene, from Season 2's Sexy, has really stuck with me. It was obvious to everyone at this point that Santana was in love with Brittany and that she was having problems with it. Choosing to sing Fleetwood Mac's Landslide (okay, so it was a cover of the Dixie Chicks' version of the song, but it was originally a Fleetwood Mac song), Santana expressed how she felt to Brittany without having to say a single word. It was very moving, and not even Santana's denial of her feelings when Rachel asked her about them later in the episode could take away from that.
Honestly, I believe that the relationship between Santana and Brittany was the healthiest on the entire series--Will and Emma have had problems from the beginning, as have Finn and Rachel, Finn and Quinn (obviously, since she slept with Puck), Puck and Quinn, Artie and Tina, Artie and Brittany, Coach Beast and Cooter (asshole), and Kurt and Blaine. Yes, they did break up at the beginning of season 4 (most of which I missed because of Hurricane Sandy--that bitch--and am only catching up with now, which is why there aren't any season 4 relationships mentioned), but it wasn't because they didn't love each other or because one cheated on the other (a problem on Glee).