Escape the apartment block raid.
Break the mini-teleporter in Kleiner's lab.
Get the crowbar.
Kill five barnacles with one barrel.
Get the airboat.
Get the airboat's mounted gun.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Destroy the hunter-chopper in Half-Life 2.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Get the Gravity Gun in Black Mesa East.
Use DOG's ball to make a basket in Eli's scrapyard.
Play through Ravenholm using only the Gravity Gun.
Kill 3 enemies using the crane.
Pin a soldier to the billboard in chapter Highway 17.
Destroy six gunships in Half-Life 2.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Use the antlions to kill 50 enemies.
Kill an enemy with a toilet.
Survive the second turret standoff in Nova Prospekt.
Gain command of a squad of rebels in the uprising.
Get through the toxic tunnel under City 17 in Half-Life 2.
Survive the generator plaza standoff in chapter Anticitizen One.
Kill all of the snipers in City 17.
Shut down the supression device by disabling its generators.
Survive the rooftop strider battle in the ruins of City 17.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Find all lambda caches in Half-Life 2.
Kill five enemies with a Manhack.
Make it to the bottom of the Citadel's main elevator shaft in one piece.
Contain the Citadel core.
Contain the Citadel core without killing any stalkers.
Use the cars to squash 15 antlions in Episode One.
Survive long enough to get on the parking garage elevator.
Help Alyx snipe 30 enemies in Episode One.
Destroy the gunship in the hospital attic.
Don't let any citizens die when escorting them to the escape train.
Escape City 17 with Alyx.
Finish the game firing exactly one bullet. Grenade, crowbar, rocket, and Gravity Gun kills are okay!
Kill five enemies with the same energy ball.
Kill an Elite Soldier with his own energy ball.
Use flares to light 15 zombies on fire.
Kill an acid antlion worker.
Squish every antlion grub in Episode Two.
Find and break every web cache in Episode Two.
Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.
Defeat both antlion guards outside the White Forest.
Run over 20 enemies with the car in Episode Two.
Survive the Hunter ambush with Alyx.
Defeat the chopper in Episode Two without any misses.
Destroy the Combine Autogun in the junkyard.
Find every radar cache in chapter Under The Radar.
Beat DOG in a race to the White Forest base.
Unlock the rocket launcher lambda cache in chapter Under The Radar.
Survive the ambush at White Forest Inn.
Send the garden gnome into space.
Secure the launch doors on missile silo 2.
Save all buildings outside the missile silo from destruction.
Save the missile silo from the Combine offensive.
Kill a Hunter with its own flechettes.
Kill 30 enemies with thrown physics objects.
Kill an enemy by planting a hopper mine.
Kill a Combine soldier with his own grenade.
Steal a Zombine's grenade.
If you are reading this achievement, Gabe Newell has successfully launched Gnome Chompski into space. If you did not also receive the achievement 'Manufacturing Ascent', Newell has abandoned his plans to shoot Noam Chomsky into space.