"They Aren't All Beautifull" off Bath for serious death-metal butt-kicking that's kept interesting by the complex structure of the song.
"Blight of River-Systems" off My Fruit PsychoBells... for the opposite: sweet (well, maybe a little bitter) pure doom with a transcendent metal coda.
"Gleam in Ranks" off Leaving Your Body Map for heroic, rallying metal (no death vox in this one).
"A Conception Pathetic", both parts of "Riseth He The Numberless"(gotta love doom-metal horns), and "Girl With A Watering Can" are all killer, too. I'd recommend getting the double-set of Bath/Leaving Your Body Map first, and if you like 'em, grab My Fruit PsychoBells...A Seed Combustible.