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.