This mod randomizes almost everything in Half-Life to give it a new, fresh way to play. You could get a hornet gun instead of the crowbar. A headcrab could be an assassin. Anything is possible, and no matter how many times you've played Half-Life, you'll never see what's coming.
There are a few options that allow you to change what's randomized. Check the advanced tab of the options menu for these, or use the console commands.
Lore Friendly (loreFriendly) - Waits to spawn certain enemies until the time they normally appear in-game. For instance, with this enabled you won't see HECU soldiers until "We've got hostiles." Random Sentences (randomSentences) - Self explanatory. NPCs can and will say anything. Random Gore (randomGibs) - Randomizes gibs and blood color for enemies...and a few other things as well... Random Text (randomTitles) - Most text displayed on the hud, such as chapter titles, credits, and instructions will be completely random.