40mm Explosive Rounds

Chris Chapter 3: 2 next to the Grenade Launcher on the 3-2 Poisawan Courtyard rooftops. Chris Chapter 4: in the bathroom of the second luxury cabin (the 5,000 SP one), with a Hand Grenade.

Grenade Launcher (Chris, Piers) and the Bear Commander's alternate fire (Jake, Sherry, Ada). 1,000 damage + 500 blast: kills J'avo and zombies in one shot.

12 or 30 per slot (sources disagree). Trick: load each round type into the launcher as soon as you pick it up; switching type does not send the loaded rounds back to the inventory, so the gun holds up to 18 (6 of each type) without using slots. Grenade Pickup Increase (22,000 SP).