Dressed For Church - "Intro (Gin Gin)"

Tune in Drop Db (C#): eb Bb Gb Db Ab Db

Riff:
   Db| 0 0  8 7 5  7 5 3  5 3 2/3
   Ab| 0 0  8 7 5  7 5 3  5 3 2/3
   Db| 0 0  8 7 5  7 5 3  5 3 2/3
[P.M.] . .  . . .  . . .  . . ./.

Just repeat this a few times.
 
Then, play it without palm muting a few times.

That's all you need to do to look hardcore. 
That and you have to have your strap really tight so that your guitar is over your chest.
And wearing Shadows Fall t-shirts will help.