Call of Duty 4 Modern Warfare
Various changes to most of the singleplayer weapons. Some are a little weird, but most are just plain fun. Unzip to CoD4/Mods. Add this to a copy of your CoD4 Singleplayer shortcut: +set fs_game "mods/ShadowMod" Including the space before +s
Here's a CoD4 single-player weapon mod by ShadowLance.