Pull Me Under was the song that I first heard, of course, but the song that made me into a life long Dream Theater fan?
Pull Me Under convinced me to buy I&W, since the band seemed to be balanced perfectly between my two favorite musical interests, heavy metal and progressive rock, but the song that made go "Holy crap I love this band"?
Surrounded.
Seriously-something about that jumped up early-Marillion meets metal riff in the verses just sucker punched me upside the head, and I fell head over heels in love with I&W. Said love of course being cemented by Metropolis and Learning to Live. But yeah, Surrounded made me into the DT fan I am today.
Go figure.