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).
This mod makes the M16A4 burst fire and the G3 semi-automatic in single-player.
Sp realism mod for COD 4.
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.
Single Player minimod for COD4. New enemy characters in US company. New explosion effects: frag grenade, rpg.
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.