I am a typical modern parent in that I try to avoid too much violent content around B, who is currently 4. Some PG and PG-13 movies are too violent for that age. For instance, N and I watched the Transformers movie a week or so ago and a mother in front of us had her 3 year old with her, and I'm sorry, but I'm not sure that was the best choice. (However, that's nothing compared to the aprocryphal story I had heard of someone viewing Hannibal, as in Hannibal the Cannibal, with their 5 year old.)
Now, I'm not all flufffy bunnies and rainbows either. We've watched some Jackie Chan; N has let B watch some Naruto and Inuyasha with her, which are both really violent actually (particularly Inuyasha); we've watched the battles in Lord of the Rings and Lion Witch and Wardrobe. In short, some violence is around and B can see it, but we try to keep things moderate at the age of 4. When B and I go to a video game store, I don't let him play or watch me play any game that involves a gun. There is absolutely no reason he needs to be thinking of guns as toys when he really is only so-so on the difference between pretending and reality.
Regardless of such parenting desires on our part, however, B plays with toy guns all the time. We don't actually have any toy guns at the house, but this is no barrier to a boy. Things which our "oh so protected from violence" child has turned into a toy gun include:
a stick bent such that one part could be a handle
a cardboard tube also bent
a flexy straw
the J.Jill catalog
the Common Birds of Hawaii brochure
There's just no stopping kids, usually boys it appears, from this stuff.
In the end, it might actually be a mistake to attempt to keep any and all violence away from children. It's like never letting a child fail, and then suddenly they enter the real world and have no idea how to cope. Instead, it's better to let the child grow into it in steps. For instance, after we watched our Jackie Chan movies, B was immediately influenced and started running around pretending to fight the bad guys, kicking and punching. And for a couple weeks at school, we'd sometimes get reports where he was doing this stuff, always as play to him, but still kicking at someone. And so we had talks about it, including things like 1) if you are going to do this, we won't be able to watch Jackie anymore at home, 2) it's only pretend fighting, and 3) they all go to fighting school to do this (by which we mean martial arts); i.e., if you want to fight for fun, you have to learn to do it with discipline.
At the time, I thought watching Jackie Chan at 4 years old was a mistake, but in hindsight I'm not so sure. There have been no such punching/kicking reports in a long time, so it seems he's learned. Every child has to go through this at some point, where they learn they can kick and then they must learn that they should not. Perhaps it is better to go through it now at 4, when the kicks don't really hurt anyone, than at 7 or 8 when they can.
Hm. This was mostly just supposed to be a funny post about B using the J.Jill catalog as a toy gun. Oh well.