Train of Thought was my first DT album. I was 15 at the time, and "Endless Sacrifice" stood out to me. There's a certain dark element in the piano, guitar and vocal during the verses, which spoke to me at the time. And, of course, the crazy piano bit in the instrumental section!
Now that I think about it, the acoustic arpeggios in the verses was the first DT guitar parts I learned to play. It was the first time I had to tune my instrument that low.