“Yes. I’m the one who discovered that the border world is EXTREMELY lactose intolerant.”:
Place a delicious wedge of Bournes pasteurised organic Cheshire cheese found in the cafeteria into the anti-mass spectrometer.
The One Free Lunch: Crowbar your way out of a barnacle’s clammy embrace.
Vent Your Spleen: Smash all the vent covers leading to air ducts.
Unnatural Causes: Cause a headcrab to jump to its death in toxic waste.
Science Be Damned!: Make the jump through the Xen portal too early.
Rock It Lawn Chair: Save your rockets until the final battle with Nihilanth.
“You are man, he is not man, for you he waits…”: Ricochet a 9mm round off G-man’s cranium whenever you meet.
Skull and CrossbOWNED: Hit 10 HECU grunts between the eyes with the crossbow in “Surface Tension”.
Observe and Report: Get 20 kills assisted by a Security Officer.
Dr. HAAAX: Have the scientist open the retinal scanner door to the grenade and handgun ammo cache for you in “Unforseen Consequences”.
Freeman’s Mines: Score 10 kills using laser tripmines throughout the game.
Back In the Day…: Beat a ragdoll with your crowbar.
Crockets? In My Black Mesa?: Kill 3 opponents with a single rocket.
That’s all for now, will think some more later…