To unlock Xbox Live Gamerscore points, complete the following Achievements.

Achievement	How to unlock
A Good Dam Fight ( 25 points )	Defeat the Battlelord on the Hoover Dam.
Air-Duke ( 30 points )	Win air hockey with a score of 7-0 in the strip club.
Annihilation ( 40 points )	Kill 100 aliens.
Balls of Steel ( 25 points )	Earn a 1,000,000 pinball score in SP.
Baron von Nukem ( 20 points )	Shoot down 20 alien fighters.
Beating the One-Eyed Worm ( 35 points )	Defeat the Energy Leech.
Big Guns, Big Ships ( 10 points )	Blow up 5 enemy gunships or dropships.
Bucket Head ( 30 points )	Find all 3 helmets in the SP campaign.
Call Waiting ( 25 points )	Listen to all phone messages.
Come Get Some ( 40 points )	Complete the SP campaign on Hard Difficulty.
Companion Barrel ( 10 points )	Unlock the secret closet at the end of the Forkstop.
Damn, I'm Good ( 50 points )	Complete the SP campaign on Insane Difficulty.
Dead Useful ( 15 points )	Kill 10 aliens with environmental explosives.
Downtown Barrel Beatdown ( 15 points )	Kill 10 aliens with tossed objects.
Drawrings ( 10 points )	Doodle something on the whiteboard in SP.
Duke Angry, Duke Smash! ( 20 points )	Kill 15 aliens with melee attacks while on steroids.
Extermination ( 25 points )	Kill 50 aliens.
FBT ( 10 points )	Get knocked down 10 times.
Flagon of Chuckles ( 5 points )	Drink a beer in SP.
Fork the Pork ( 10 points )	Kill 6 aliens with the forklift.
Freeze Well! ( 20 points )	Kill 15 frozen aliens.
Gunslinger ( 50 points )	Carry the gold pistol through the whole SP campaign.
He's Got a Hologram! ( 5 points )	Use a Holoduke in SP.
Hippy-Stomper ( 20 points )	Foot stomp 12 aliens.
I Am All That Is Man ( 40 points )	Discover all Ego cap awards.
I Need a Date ( 5 points )	Look at every page of a calendar in SP.
I Need a Towel ( 10 points )	Get hit by 10 Pregnator bombs.
Judge, Jury, Executioner ( 20 points )	Execute 20 aliens.
Juiced ( 5 points )	Take steroids in SP.
Let's Rock ( 30 points )	Complete the SP campaign on Normal Difficulty.
Lots of Whacking ( 25 points )	Win a game of Alien Abortion in the strip club.
Natural Disaster 3x ( 10 points )	Kill 3 aliens at once.
Nobody Likes a Whiner ( 5 points )	Knock out the talent at the talk show.
Noms ( 10 points )	Eat 10 pieces of food during the SP campaign.
Not Bad for a Human ( 40 points )	Defeat the Alien Queen.
Nuclear Devastation ( 50 points )	Kill 250 aliens.
Octacide ( 25 points )	Defeat the Octaking.
On the Noggin ( 25 points )	Kill 30 aliens with headshots.
One-Eyed Freak ( 10 points )	Defeat the Cycloid.
Party Animal ( 10 points )	Drink all of the beers in the strip club.
Pescaphobe ( 10 points )	Kill all the catfish in the underwater level.
Piece of Cake ( 20 points )	Complete the SP campaign on Easy Difficulty.
Pit Champion ( 25 points )	Defeat the Battlelord in Las Vegas.
Road Rage ( 20 points )	Kill 15 aliens with the monster truck.
Special Thanks ( 5 points )	Watch the credits all the way through.
Sticky Bomb Like You! ( 10 points )	Put a Trip Mine on a live alien.
Substance Abuser ( 10 points )	Drink beer while on steroids or vice versa in SP.
Sunday, Black Sunday ( 5 points )	Shoot down the blimp above the stadium.
Trapper ( 20 points )	Kill 10 aliens with Trip Mines.
Turd Burglar ( 10 points )	Find and steal a piece of poo.