Find all lambda caches in Half-Life 2.
Keep Off the Sand!
Cross the antlion beach in chapter Sandtraps without touching the sand.
Play through Ravenholm using only the Gravity Gun.
Kill five enemies with a Manhack.
Kill an enemy with a toilet.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Kill all of the snipers in City 17.
Use DOG's ball to make a basket in Eli's scrapyard.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Pin a soldier to the billboard in chapter Highway 17.
Break the mini-teleporter in Kleiner's lab.
Kill 3 enemies using the crane.