Well, the other tabs for this song are just plain wrong, so here's my take on the main 
(and what a riff it is).

Tabbed by Ashley Webster.
And don't plagiarise people, it helps no-one.

Standard Tuning (You should all know what that is :P)

Main Riff:
  A5
-------------------------------------------------------------------------|
-----------------------------------------------------------repeat--------|
-------------------------------------------------------------------------|
--7\4----7-7-7\4----7-7-7\4----7-7---0-0-4-5---------7\4-----------------|
--7\4----7-7-7\4----7-7-7\4----7-7-----------3-3-5/7-7\*|
--5\2p0--5-5-5\2p0--5-5-5\2p0--5-5-------------------5\2-----------------|

The slides on the initial powerchords aren't precise, just aim to slide off towards the 
or 2nd fret and then do a pull-off very quickly. Also, the powerchords can be played as 
notes, but I find the powerchords give it a little more power.

Verse:
 A5                               F5  G5
-------------------------------------------------------------------------|
------------------------------------------------------------repeat-------|
-------------------------------------------------------------------------|
--7-------------------------------3---5-----------7----------------------|
*|
--5-------------------------------1---3-----------5----------------------|

Not written out the strumming pattern here, but it's easy to work out. Well, that should 
you the general idea. Riff away!