Max Brooks, in his Zombie Survival Guide explains how he favors the AK-47 and assault rifles like it over the M series weapons. I've heard this sentiment before, and figured that these people probably had some point.
Then- I got to shoot an M4- and I must admit that I was impressed. The weapon is light- which works well for survivors on the move, and more over, it was the easiest to handle firearm that I have ever held. It fires accurately with very little kick.
It was almost like shooting a very good .22 rimfire weapon- low kick, good accuracy. But then the holes in the target were significantly larger.
Now, I didn't have to clean or disassemble the thing, but in a situation where the only shots that count are head shots, I'd definitely go with an M4 over something with more kick and less accuracy.
Anyway, I am now completely on board with the most popular assault rifle used by wedding cake toppers.
Here are two couples who decided that the M4 was the best way to dispatch the zombie horde.
And here are a few of the zombies that I've made to invade wedding cakes.