I just added a particle feature where you can shoot zombies with the bazooka, and they will explode into zombie body parts. Blood trails follow them around as they bounce of walls and players for a few seconds before they disappear. Here's a few screenshots...
Yeah the bazooka is pretty much finished too. The rocket is 360 degrees and there's a pretty nice smoke trail that follows it as well The buttons on the left are for debug. They obviously wont be in the real game.
If you want to see the particle system in action, I also used the same feature in one of my older games "The Last War". Even though that was a side view scroller game, it has the same concept...
Here's the video by the way. Some things were fixed in Zombie Swarm such as the blood actually being on the body parts.