I like the all the songs on the soundtrack!
If I had to pick ONE song, I'd choose Spotlight from Mutemath simply because I love where/how its used in the film...I get all giddy thinking of Edward opening the door of his car for Bella, walking through the parking lot. Its also used in the scene on the large boulders, near the lake, where Edward answers Bella's questions.
Have any of you purchased the Twilight SCORE? Its great as well! I'm able to "watch" the film in my head while listening to it! It was hard to find the score the week of Christmas, everyone was out!