Call of Duty 4 Modern Warfare
This mod makes the Arab OpFor have a mix of Russian weapons (AK-47, RPD, RPG, etc.) with American and German weapons (M16, M4(rare), M16 Grenadier, G3).
Here's a cool new weapon mod for Call of Duty 4 single-player by Wjj91. The mod focuses on reducing ammo counts and other aspects of the weapons, as well as modifying the skins somewhat.
This mod makes the M16A4 burst fire and the G3 semi-automatic in single-player.
Sp realism mod for COD 4.
Single Player minimod for COD4. New enemy characters in US company. New explosion effects: frag grenade, rpg.
This is single player mod. It's changing all weapons (not in snipers mission) in missions to AK47.
Here's a CoD4 single-player weapon mod by ShadowLance.