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

Unlockables

99 Red Balloons (15 GP) 99 Red Balloons - Kill 10 enemies while they are in an anti-gravity bubble.
Big Bang (30 GP) Big Bang - Destroy a Knight using a grenade.
Bird of Prey (15 GP) Bird of Prey - Kill 25 footsoldiers using your rocket pack guns.
Blind Luck (15 GP) Blind Luck - Kill one of each enemy footsoldier using blind fire.
Blue Light Special (15 GP) Blue Light Special - Kill 3 enemies with one grenade.
Bookworm (30 GP) Bookworm - Find all journals.
Breaking Camp (30 GP) Complete Breaking Camp.
Captain of the Ship (15 GP) Captain of the Ship - Destroy 10 enemy aircraft while yours is on fire.
Cleanup on Aisle Three (15 GP) Cleanup on Aisle Three - Kill 100 enemies with headshots.
Cliffhanger Killer (15 GP) Cliffhanger Killer - Kill 50 enemies while in vertical cover.
Crash Site (15 GP) Complete Crash Site.
Dark Void (100 GP) Complete Dark Void.
Dear Diary (15 GP) Dear Diary - Find a journal.
Death from Above (15 GP) Death from Above - Kill 50 enemies while hovering.
Defending the Ark (15 GP) Complete Defending the Ark.
Demolition Derby (30 GP) Demolition Derby - Collide with another UFO 10 times.
Fireworks (15 GP) Fireworks - Kill 10 airborn enemies using grenades.
Float Like a Butterfly (20 GP) Float Like a Butterfly - Escape from 10 melee attacks.
Forgot My Tow Cable (15 GP) Forgot My Tow Cable - Fly through an Archon's legs.
Get Your Feet Wet (15 GP) Get Your Feet Wet - Buzz the water.
Grand Theft...UFO? (15 GP) Grand Theft...UFO? - Hijack 20 UFOs.
Grease Monkey (30 GP) Grease Monkey - Upgrade all weapons.
I'm a Rocketman, Baby (15 GP) I'm a Rocketman, Baby - Perform 100 special maneuvers with the rocket pack.
Into the Void (30 GP) Complete Into the Void.
Killing Spree (20 GP) Killing Spree - Kill 10 enemies within 60 seconds.
Light Up the Sky (30 GP) Light Up the Sky - Destroy 25 targets with the Ark's AA guns.
Mark of the Adept (15 GP) Mark of the Adept - Destroy 5 UFOs in the Prologue.
Master of Arms (15 GP) Master of Arms - Kill an enemy with every rifle weapon.
Pack Rat (30 GP) Pack Rat - Acquire 30,000 Tech Points.
Prison Escape (15 GP) Complete Prison Escape.
Prologue (15 GP) Complete Prologue.
Prophesied One (15 GP) Complete Prophesied One.
Rochambeau, I Go First (15 GP) Rochambeau, I Go First - Kill 50 enemies with melee attacks.
Rocket Clothesline (15 GP) Rocket Clothesline - Melee an enemy immediately after landing.
Spare Parts (15 GP) Complete Spare Parts.
Terminal Velocity (15 GP) Terminal Velocity - Free fall for 10 seconds.
Tesla's Apprentice (15 GP) Tesla's Apprentice - Upgrade first weapon.
The Collector (15 GP) Complete The Collector.
The Devastator (30 GP) The Devastator - Destroy 25 UFOs while piloting a Survivor fighter.
The Revolt (15 GP) Complete The Revolt.
The Squishy Center (20 GP) The Squishy Center - Kill a Sarpa piloting an Archon.
The Survivors (15 GP) Complete The Survivors.
The Village (15 GP) Complete The Village.
Those Aren't Fortune Cookies (15 GP) Those Aren't Fortune Cookies - Step on 10 slugs.
Tower of Return (30 GP) Complete Tower of Return.
Ultimate Bad Ass (60 GP) Ultimate Bad Ass - Complete Dark Void on Hardcore.
Village Attack (15 GP) Complete Village Attack.

Upgraded Radar - To unlock an upgraded radar that shows the location of Tech Point Caches, Ammo Caches, Weapons Lockers and Journals, complete the game for the first time.