Heavy songs by "less-heavy" bands

What are some heavy songs by artists not really known for heavy rock? Rez Band were always on the lighter, bluesier side of hard rock, but then they put out this song:

(All because Im in the Disciple mood)

Disciple is that heavy compared to other bands of the scene they were in
but this is by far their heaviest song

Petra-Jeckyll & Hyde
https://www.youtube.com/watch?v=LVmKHYCO554
and
https://www.youtube.com/watch?v=vBQOCCGJ4U4

WildWorld wrote:What are some heavy songs by artists not really known for heavy rock? Rez Band were always on the lighter, bluesier side of hard rock, but then they put out this song:

I always thought that the heavier sound on that album was a result of touring with Sacred Warrior the year before.

The best example I can think of is Kohllapse.  
Normally a "Type O" genre style doomy groove metal with clean vocals and often no distortion at all.

...and then there was this track.