I could never choose a favorite song, permanently. I'm not really a fan of choosing 'favorite' anythings.
But, this song comes to mind, for now at least. Loved it consistently for the past couple of years, once it grew on me after a few hearings.
One of those songs that I wouldn't change any aspect of, given the chance, every moment of it is just, on point, for me. The roaring, triumphant sounding guitars, the chaotic, intense drumming, with the shouting, breathless vocal performance, it all layers together into such dense, dreary, distorted, satisfyingly overwhelming noise. I really like the way the song progresses from start to finish, each section lasts just the right amount of time, and transitions in a great way.
The lyrics are what really brings it together for me, though. I suppose everyone interprets lyrics differently, so they appeal to some much more than others, but in general, they're dark, pleasingly vague, there is some awesome imagery, and while openly about suicide, depression, misery, like many songs, I think what sets them apart here is the tone and delivery. It's sad, but in a bitter, fed up, uncaring, genuine way. They sound ambivalent, like they're coming from someone who no longer cares about hope, or getting better, life or death, they are just tired, and ready for the end. Its cathartic, too, in the context of the album, the final song, about death, release, after an hour and a half of music dealing with insanity and suffering and fear.
Can't really describe why I like it so much, though. It just sounds so massive and grand, beautiful and ugly at the same time.