This is going to be really tough, because this is one of those albums for me where every track is top-notch. I think just by default for me it's between The Path and As Death Embraces, because even though they're not significantly less good than the other tracks, they're simpler and so perhaps not as rewarding(?).
I'm going to vote As Death Embraces right now, because I think that's the one I would miss least if it were to suddenly pop out of existence.