Ooh, tough question.
Pink Floyd should probably get about a dozen points on this subject. I've always found the guitar work in "Dogs" to be jaw dropping to name one out of many.
Tears For Fears has a song called "Sketches of Pain" which works with some great accoustic guitar layering that I absolutely love as well.
The Flower Kings have a song on their Space Revolver cd called "Rumble Fish Twist". There's two sections to this song, the first is a peppy goofy bit, and the second is a sort of moody and dark yet beautiful piece.
A few other random choices: "Something" by the Beatles, "Lay it Down" by Spock's Beard, "Telegraph Road" by Dire Straits, "Back to Good" by Matchbox20, "Man on the Corner" by Genesis, "Wait for Sleep" by Dream Theater, and yes..."My Everafter" by Enchant. =)
I'm not including the "George Winston" style music, although there's a lot of stuff out there I really, really love...when I'm in the mood for it.