Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Northwest Master (20 points): Complete hunting in 4 regions.
Southwest Master (20 points): Complete hunting in 8 regions.
East Master (20 points): Complete hunting in 12 regions.
West Master (20 points): Complete hunting in 16 regions.
South Master (20 points): Complete hunting in 20 regions.
Bronze Sharpshooter (100 points): Complete the game with a minimum of Bronze on all missions.
Silver Sharpshooter (150 points): Complete the game with a minimum of Silver on all missions.
Gold Sharpshooter (200 points): Complete the game with a minimum of Gold on all missions.
Gun Buff (50 points): Unlock all weapons.
Upgrade Pro (50 points): Earn all unlockables in the game.
I Have the Power (10 points): Use all Power-ups at least once.
Deer Slam Cup (10 points): Complete the Deer Slam.
Turkey Slam Cup (10 points): Complete the Turkey Slam.
Waterfowl Slam Cup (10 points): Complete the Waterfowl Slam.
Upland Bird Slam Cup (10 points): Complete the Upland Bird Slam.
Small Varmint Slam Cup (10 points): Complete the Small Varmint Slam.
Large Varmint Slam Cup (10 points): Complete the Large Varmint Slam.
Predator Award (10 points): Use the Thermal Cam 10 times.
Peeping Tom Award (10 points): Use the Xrayl Cam 10 times.
Molasses Award (10 points): Use Slow Time 10 times.
Chillax Award (10 points): Use Freeze Animal 10 times.
Cats Award (10 points): Use Laser Bullet 10 times
McGraw Award (10 points): Use Quick Draw 10 times.

Additionally, there are eight secret achievements:

Huge Tracts of Land (20 points): Hunting in 20 regions has been completed.
Arcade Master Gold (50 points): Gold has been taken in all arcade missions.
Acme Lost a Customer (25 points): A maximum integrity, five-star Large Varmint, has been taken.
Check Out That Rack! (25 points): A maximum integrity, five-star deer, has been taken.
Don't Drive Angry (25 points): A maximum integrity, five-star Small Varmint, has been taken.
Is That Howard's Cousin? (25 points): A maximum integrity, five-star Waterfowl bird, has been taken.
It's Raining… Hen (25 points): A maximum integrity, five-star Upland bird, has been taken.
Thanksgiving Dinner (25 points): A maximum integrity, five-star turkey, has been taken.