I suppose the easier thing to do is just have the Trustee (or successor) sell them on your death and distribute the proceeds to the beneficiaries. Why go through the hassle of trying to transfer them to individual heirs unless you know your son, daughter, etc. really, really, really wants it? Well, I'm basically referring to machine guns.
Silencers? What if the Trust has several well used, outdated (old tech) silencers when you die? This could be like getting rid of a rusty old car muffler coated in toxic waste that nobody wants! What then?