Disappear - I agree, just one hauntingly beautiful song.
The Best Of Times - of course, one of the most personal songs by DT, maybe THE most personal.
Octavarium - my fav song of all time (with Supper's Ready & Gates Of Delirium), the final solo always leaves me speechless.
Illumination Theory - only because my ex-gf used to love this song, hard to listen to it now, what a shame.