I wouldn't count "Erotomania" either, since it's part I of a suite. Still, interesting thread.
My favourite has always been "Stream Of Consciousness", which is also my favourite track on Train Of Thought. To me, "SOC" is special - for one, it's the only 'long', 10+ minute instrumental by the band. Still, it doesn't feel boring at any point. There are many cool, interesting sections in it (such as the salsa-ish bit in the middle, and the proggy organ-like keyboard melodies towards the end). That said, to me a listen is not complete without "Vacant" first.
The rest? "Dance" and "Kitchen" are amazing in different ways.
I also like "1928", "2285", and "Dystopian" a lot, but they are really collages of melodies / progressions from other songs.