Black Mesa

Brownian Motion

Common63.6%

Pass the toilet paper to the Scientist in need.

Convection Refinement

Common54.3%

Ruin the microwave casserole.

Gray Matter Propulsion

Common44.8%

Headshot 20 Enemies with the .357 Magnum.

Prophylactic Suggested

Uncommon37.9%

Get overtaken by a Headcrab's ample anterior.

Caffeine Extraction

Uncommon29.4%

Perform surgical caffeine extraction from 20 vending machines.

Centripetal Attraction

Uncommon25.0%

Kill 20 Enemies with the Hivehand.

Permeable Infrastructure

Uncommon25.0%

Use the alternate path in Office Complex.

Inflammatory Actions

Uncommon21.6%

Kill a Headcrab using fire.

Quantum Capacitance

Uncommon21.1%

Overcharge it anyway.

Proverbial Tinkerer

Uncommon19.7%

Interfere with the alarm and laptop in Anomalous Materials.

Dead Reckoning

Uncommon18.7%

Kill an Assassin with the .357 Magnum.

Premature Expulsion

Uncommon14.8%

Use an entire clip of Gluon ammo in one continuous shot.

Mega Hertz

Uncommon13.9%

Kill 5 Enemies with one Grenade.

Calculated Trajectory

Uncommon12.0%

Kill 10 airborne Headcrabs using the Shotgun.

Universal Gravitation

Uncommon12.0%

Get killed by your own Snarks.

Remote Detonation

Uncommon10.8%

Kill a Barnacle with a Satchel.

Resonance Procrastinator

Uncommon10.8%

Refuse to insert the specimen into the Anti-Mass Spectrometer.

Nuclear Fishin'

Uncommon10.4%

Kill an Ichthyosaur with either the Tau or Gluon.

Digital Wizardry

Rare9.7%

Kill 10 enemies with a reprogrammed Sentry.

Futile Resistance

Rare7.7%

Kill 10 Enemies with Snarks.

Hyper Saturation Conundrum

Rare7.5%

Drown in Lambda Core's coolant.

Ethically Questionable

Rare7.4%

Conduct all of the questionable research experiments.

Unified Coupling Theorum

Rare5.9%

Help the Barnacle and Headcrab find true love.

Anti-Matter Over Mind

Rare5.1%

Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.

Kinetic Repulsion

Very rare4.9%

Kill a Marine with their own Grenade.

Limitless Potential

Very rare3.1%

Accept G-Man’s offer of employment.

Rare Specimen

Very rare2.9%

Send the Hidden Hat to Xen.

Well-Done

Very rare2.6%

Cook a Grenade for too long.

Rather an Anticlimax

Very rare2.0%

Decline G-Man’s offer of employment.

Less Than Desirable Consequences

Very rare1.9%

Die in the AMS Beam before starting the experiment.

PhD in Pacifism

Very rare1.4%

Don't kill any Vortigaunts in the Borderworld.

Stealth Technology

Very rare1.3%

Escape the Hangar in Surface Tension without alerting the Soldiers.

One Step Ahead

Very rare1.0%

Kill 10 Enemies with Tripmines​​.

Our Brains And Your Brawn

Ultra rare0.8%

Assemble all the possible Scientists and Guards at the end of Office Complex.

Gonad Glider

Ultra rare0.7%

Get whacked into oblivion in the ledge fight.

Orbital Trajectory

Ultra rare0.5%

Skip the opening Xen island with a secret jump.​

Black Mesa Decathlon Winner

Ultra rare0.4%

Escape the Gargantua’s Lair without taking any damage from Gargantuas.

Doctor’s Signature

Ultra rare0.4%

Deliver the finishing blow to Gonarch with your Crowbar.

Late for Work

Ultra rare0.3%

Defeat Nihilanth in under 4 minutes.​

Specimen GG

Ultra rare0.3%

Take out all three Healing Crystals in Nihilanth’s Chamber at the same time​.

Laser Immunization

Ultra rare0.2%

Complete Interloper without taking any laser damage.

Post-Mortem Interval

Ultra rare0.1%

Find each member of the missing research teams.

Prolific Popper

Ultra rare0.1%

Kill all Protozoans in the Borderworld.