A simple script with a 'readme' file and installation instructions. It makes the game a ton more challenging and fun.
Installation: Copy skill.cfg and go to your Half-Life 2 directory. Go to 'hl2' then 'cfg' and paste it there.
All damage values have been changed to make the game more challenging. For example: A shotgunner can absolutely obliterate you if you have low health. Out of cover two enemies with SMGs or AR2s can gun you down quickly. However all your weapons deal the same amount of damage as their's. The shotgun is now 12 gauge, you can tell if you count the holes in the wall.
To kind of make up for the high damage rates, all supply crates are now randomized. From my experience they mostly drop health or suit energy. I even got a grenade once.
Melee enemies also have a damage boost. Zombies can now take down half of your health if you have no shields. Poison zombies can be killed with one or two shots from a shotgun or even one to two grenades. Fast zombies wear you out if you manage to be overwhelmed. Since gameplay-wise Headcrabs are inconsistent I decided to sort of make up for it with a bit higher damage. Also zombies are no longer bullet spongy.
Damage values with body parts on both the player and NPCs have been adjusted. Heads are the weakest part now, one shot to the head will end any bipedal enemy. Legs are the second weakest. It should take one to two shots to legs before they drop. The stomach uses the same value as the legs. The torso is the strongest part, it should require three to four shots from anything but a shotgun to kill it. Antlions and aerial vehicles are exempt from these factors.
Aerial vehicles should be the only thing you worry about. The hunter chopper in Water Hazard can be a bit brutal at times. This is made up for since the boat gun deals more damage. Gunships shouldn't be too much of an issue as long as you take cover and maneuver your rockets.
You also carry a bit more ammo for the pistol, SMG, AR2, rocket launcher. Also can carry more grenades.
Credit to Memelord for reviewing this.