I find that the heavier types of rock invoke the more war-friendly emotions in people, so while the whole song might not be something you'd want to sing, perhaps taking little snippets from songs would preserve your badassery while still avoiding the death metal sound.

Some of my favorites:

"Take this life, I'm right here! Stay awhile and breathe me in!"
-Take this life, In Flames

(This one is a little mixed for appropriateness)"It's not that complicated and you ain't gotta believe
They'll put me down in a hole before I let you succeed
I've never been complacent, I can't afford to be
I know you think you're special but you ain't nothin'
Hope I'm on the list of people that you hate
It's time you met the monster that you have helped create!"
-Meet the Monster, Five Finger Death Punch

(Good for when you have an army)
"We fight until no one can fight us
We live, and no one can stop us
We pull when we're pushed too far
And the advantage is
The bottom line is
We never, had to fight in the first place
We only, had to spit back at their face
We won't, walk alone any longer
What doesn't kill us only makes us stronger
We-we are the new diabolic
We-we are the bitter bucolic
If I have to give my life you can have it
Say it again say it again (we won't die)(x4)"
-Pulse of the Maggots, Slipknot

(Another good one for war marching)
"You're here because
You're one of us
We are the strength
We are the soldiers
You've conquered pain
You've conquered fear
Stand proud and salute
The bloodied flag here
We fear not our mortality
We'll serve to the best of our ability
We give our lives to our masters
We vow to smite our enemies"
-The Gears, Dethklok

P.S. Sorry if this post is too long, but I get very enthusiastic when music is involved.

P.P.S. Also sorry if none of this interests you...