When Dream and Day Unite: Afterlife
Images and Words: Take the Time
Awake: Caught in a Web
Falling Into Infinity: Lines in the Sand
Scenes from a Memory: Home
Six Degrees: Misunderstood
Train of Thought: Stream of Consciousness
Octavarium: Panic Attack
Systematic Chaos: In the Presence of Enemies
Black Clouds and Silver Linings: The Count of Tuscany
A Dramatic Turn of Events: Bridges in the Sky
Dream Theater: Surrender to Reason
I don't really have a clear favorite on DT12; Surrender to Reason was just the first song I thought of, so I went with it.
Train of Thought is a tough call for me; Stream of Consciousness and In The Name of God are some of my favorite songs ever, so it's hard to choose between them.
Scenes from a Memory is also a weird one for me. I went with Home, but really, my favorite piece of music on the album is definitely Scene Two. Together, Overture 1928 and Strange Deja Vu are magic. However, I rarely listen to one without the other, so if I can't count them as one piece, I feel weird picking either of them. So, Home it is.
The rest of the albums are pretty easy for me.