Halo Combat Evolved
Jackle's Modded Gephyrophobia
To install, click on the mirror of your choice, it will give you the option save or open, press save and now you should be in My Computer, now got to Local Disk (C:) and choose program files, then Microsoft games, now it’s extremely obvious, click on
This mod adds several tweaks/changes to the game. For example, shotguns shoot half a dozen rockets, assault rifles shoot Fuel Rod plasma, Turret Warthogs fly, you can walk on walls and take no damage from falls.