Half-Life 2

Defiant

Hidden achievement

Submissive

Hidden achievement

What cat?

Break the mini-teleporter in Kleiner's lab.

Barnacle Bowling

Kill five barnacles with one barrel.

Vorticough

Discover the hidden singing vortigaunt cave in chapter Water Hazard.

Blast from the Past

Find the HEV Suit Charger faceplate in Eli's scrapyard.

Two Points

Use DOG's ball to make a basket in Eli's scrapyard.

Zombie Chopper

Play through Ravenholm using only the Gravity Gun.

Hallowed Ground

Hidden achievement

OSHA Violation

Kill 3 enemies using the crane.

Targetted Advertising

Pin a soldier to the billboard in chapter Highway 17.

Where Cubbage Fears to Tread

Hidden achievement

One Man Army

Destroy six gunships in Half-Life 2.

Keep Off the Sand!

Cross the antlion beach in chapter Sandtraps without touching the sand.

Bug Hunt

Use the antlions to kill 50 enemies.

Flushed

Kill an enemy with a toilet.

Counter-Sniper

Kill all of the snipers in City 17.

Atomizer

Disintegrate 15 soldiers by throwing them into a Combine ball field.

Lambda Locator

Find all lambda caches in Half-Life 2.

Hack Attack!

Kill five enemies with a Manhack.

Watch Your Head!

Make it to the bottom of the Citadel's main elevator shaft in one piece.

Containment

Contain the Citadel core.

Pacifist

Contain the Citadel core without killing any stalkers.

Car Crusher

Use the cars to squash 15 antlions in Episode One.

Elevator Action

Survive long enough to get on the parking garage elevator.

Live Bait

Help Alyx snipe 30 enemies in Episode One.

Attica!

Destroy the gunship in the hospital attic.

Citizen Escort

Don't let any citizens die when escorting them to the escape train.

Escape From City 17

Escape City 17 with Alyx.

The One Free Bullet

Finish the game firing exactly one bullet. Grenade, crowbar, rocket, and Gravity Gun kills are okay!

Conservationist

Kill five enemies with the same energy ball.

Think Fast!

Kill an Elite Soldier with his own energy ball.

Zombie-que

Use flares to light 15 zombies on fire.

Acid Reflex

Kill an acid antlion worker.

Get Some Grub

Squish every antlion grub in Episode Two.

Piñata Party

Find and break every web cache in Episode Two.

Into the Breach

Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.

Twofer

Defeat both antlion guards outside the White Forest.

Hit and Run

Run over 20 enemies with the car in Episode Two.

Meet the Hunters

Survive the Hunter ambush with Alyx.

Puttin' On a Clinic

Defeat the chopper in Episode Two without any misses.

Gunishment!

Destroy the Combine Autogun in the junkyard.

Cache Checker

Find every radar cache in chapter Under The Radar.

Pedal to the Metal

Beat DOG in a race to the White Forest base.

Gordon Propelled Rocket

Unlock the rocket launcher lambda cache in chapter Under The Radar.

Quiet Mountain Getaway

Survive the ambush at White Forest Inn.

Little Rocket Man

Send the garden gnome into space.

Secondary Silo Secured

Secure the launch doors on missile silo 2.

Neighborhood Watch

Save all buildings outside the missile silo from destruction.

Defense of the Armament

Save the missile silo from the Combine offensive.

Payback

Kill a Hunter with its own flechettes.

Bone Breaker

Kill 30 enemies with thrown physics objects.

Deadly Harvest

Kill an enemy by planting a hopper mine.

Hot Potat0wned

Kill a Combine soldier with his own grenade.

Grave Robber

Steal a Zombine's grenade.

Gnome Alone

Launch Half-Life 2 after Gabe Newell launched a garden gnome into space.