Well, Credence was the first one I heard, so it's been in my head the longest. Then To Bid You Farewell, Then Face of Melinda, etc. I think the ending of Face of Melinda is fantastic, the heavier parts have a glorious harmony to them. But few things will ever really top To Bid You Farewell. From the catchy "Fade to Black" intro, to the nice, somewhat complicated dual guitar work (I still can't figure out where one guitar stops and the other starts, so I play what appears to be the most prominent melody throughout the riff). It slows down to comfortable level before gearing up into the distorted section - and that first distorted riff remains one of my all-time favourites. The next part just carries you along, and I tend to picture the guitars going at once onstage, even though they don't play this one live. Just totally into it. Then it calms, calms.. Until the drums stop, and just a simple harmony is left, and haunting lyrics. Can't get enough of this song. Like I think I said before somewhere, a non-Opethian friend of mine made me wait in the parking lot while we listened to the heavy riff. "Hold on.. this riff really kicks ass.." We waited till the end of the song.