Clive Barkers Jericho

Use Black's grenade launcher for this (left trigger). Try not to get too close to what you're shooting as you'll kill yourself although it will still count the enemy kill. If you use Black as much as possible through the game you should get this easily by the end. Reload an early level if you haven't.

Start up lvl Skin. It will just be you (Black) and Jones. Right away Black starts running towards a guy throwing balls of flame, switch to Black and stay/run back in the doorway area that you start in. Face the open doorway and let Jones run out so they flame throwing guy downs him. The best place I found was in the back left corner (facing the doorway). The flame guy won't throw the flame balls at you if you get there quick enough so he won't be a problem. He spawns infinite cultists. They will come 1 at a time and right when they get in the doorway, blast 'em with the grenade launcher. You will want your reticle about eye level and slightly left of mid doorway. After ammo runs out, die and restart, all kills count. They spawn about 15 seconds apart, it won't take long. You can also get all your ghost kills and head shots here as well.