Wish - Nine Inch Nails

combine Et Tu Brute's whole demo into one song, and that would be it.

The Crusade - Trivium. I would recommend it greatly. Especially if you're the kind of person who's into "lots and lots of guitar chords"

Listen to "Wake" by Rosetta....the buildup and climax of the song are so intense...I could probably recommend a lot of Isis songs here too

oh comely - NMH
true love - elliott smith
orchard - indian summer
slow and steady wins the race - pedro the lion

Almost anything by Rage Against the Machine will definitely get you going. Especially if your listened to the fueling lyrics.

Hurt - nine inch nails

uh,
pretty much an kamelot song,
and manniquin (i totally spelt that wrong) by cradle of filth
& all 3 versions of nymphetamine by cradle of filth

If you're talking "heaviest" song(s) ever, give the grind band Slough's demo a listen. I'm a massive grind aficionado, and I still haven't found anything as crushingly heavy and disturbing.

Emotionally "intense"? Give My Dying Bride's Turn Loose The Swans a listen (more specifically, the song "Crown Of Sympathy"). You might find it goofy, but you may as well try it out. That, or the live version of Indian Summer's Angry Son.
It's a little painful, actually.

Mogwai - Like Herod