I was gonna vote for my usual, but seeing as Jerusalem is getting so many votes, I've changed my mind.
Chemical Wedding
Book of Thel
Myself
Even though KDH is actually my #4 from this list.
Regarding Book of Thel, when I first heard TCW, it was actually the only song I really liked from the album. However, usually songs I like right away have a faster burn rate, so I'm just burned out on Thel. It's still a great tune, though, and I honestly wouldn't mind seeing it win.
Darkside of Aquarius is another song that I loved right away (even ranked it as my absolute favorite Bruce song) that burned on me, but I took a break from it, and now it's back to being my #2.