M16 family are commonplace. There's other freebies, of variable quality, all over the place, some good, some rather blatantly out of scale, some a heap of rubbish. You're not limited to Poser. There are 3DS and Lightwave freebies out there, though they need a bit of work, sometimes. As for an actual Kalashnikov, there's a good model here as a freebie: search for "gun" and it's on the second page. I recall it being suggested that it's the Girl Scouts who are entrusted with controlling nuclear weapons release. See Simon Barber's Road Runner for an explanation, downloadable here. Yes, I do have a warped mind.