In Quake II, Bullets are used to supply both the Machine Gun and the Chain Gun, and are found in boxes of 50. Machine Gun Guards, Enforcers, Gunners, Tanks and Tank Commanders sometimes drop Bullets when killed.

Quake II
Organization		Terran Coalition of Man · Strogg
Characters		Bitterman · Viper · Willits
Expansions		The Reckoning · Ground Zero · Call of the Machine
Enemies		Light Guard · Machine Gun Guard · Shotgun Guard · Barracuda Shark · Enforcer (Infantry) · Berserker · Gunner · Gunner Commander · Flyer · Parasite · Mutant · Brains · Medic · Icarus · Technician · Gladiator · Iron Maiden · Arachnid · Tank · Tank Commander
Bosses		Super Tank · Hornet · Guardian · Jorg · Makron
Weapons		Blaster · Shotgun · Super Shotgun · Machine Gun · Chain Gun · Grenade · Grenade Launcher · Rocket Launcher · Railgun · Hyperblaster · BFG10k · Grappling Hook
Ammo		Bullets · Shells · Grenades · Rockets · Slugs · Cells
Powerups		Armor (Armor Shard · Jacket Armor · Combat Armor · Body Armor) · Health (Stimpack · Medikit · Megahealth · Adrenaline) · Ammo Pack · Bandolier · Enviro-Suit · Invulnerability · Key · Quad Damage · Rebreather · Silencer · Power Shield
Hazards		Blaster Trap · Electric Track · Explosive Barrel · Explosive Crate · Fall · Laser · Lava · Slime · Teleporter · Vacuum · Water
Barriers		Force field
Vehicles		Drop Pod · Phobos