Not trying to be a jerk, but Nerf grenade launchers have been made.
I saw one at my campus last night during the kick off. The one I saw just fired a big foam grenade, which wasn't very effective.
This kid made one that disperses into darts somehow.http://www.youtube.com/watch?v=nHKLtwecJN0
I watched the actual firing portion about five times. So far as I can tell, the darts just fall out when it hits the ground.
Random two cents to add: It's really not that hard to lead a good zed charge if you notice nobody else stepping up to the task. You just have to have two things: the knowledge of when to charge, and a loud enough voice to reach all within the combat zone. Calling a charge at the wrong point (up a hill at a superior force) can be worthless. Not having a loud enough voice leads to only half the force charging, which is easily stopped.
Our final mission (not last stand) had a great example of the above. All semester zombies had been lacking in solid leadership. I'd be zombified the night before via a trapdoor, so this was my first experience on the zed side this semester. We initially had a fail charge because the guy that called it a.) didn't know what he was doing, and b.) wasn't loud enough. Zeds had encircled a large human group, but were very spread out. The charge was called, but only half the circle charged, and only haphazardly; everybody was stunned, with no kills. Later in the mission, though, we got our revenge. Humans had entered a small grassy patch (we held off on charging while they exited the street and parking lot areas), and I noticed everyone milling about, nobody taking charge. I thought, what the hell, why not,
and screamed at the top of my lungs, "ZOMBIES! We are CHARGING in THREE, TWO, ONE, CHARGE!" A beautiful charge resulted. Yeah, I took one of the first darts, but meh, such is the life of a charge leader.
In summary, to lead a good impromptu zed charge:
1.) Know when to charge; 30 zeds encircling 50 humans is not a good charge point. 40 zeds encircling 20 humans is.
2.) Be loud enough that all zeds in the combat area can hear you.
3.) Offer enough time that everyone can understand what they're about to do. A simple "Charge!" will have zeds hesitate, leading to a fractured charge. A long, drawn out charge call will allow everyone to position themselves and pick targets, as well as freaking out the humans who know a charge is about to come.
Seriously though. Lead charges. Watching hordes of people descend upon puny human mobs because you told them to
is one of the most awesome feelings in the game, and way better than getting a couple kills. I gladly take the first couple darts in a charge for that reason.