Back when I was a kid, the sight of toy guns never fazed me, and it was easy to disassociate child's play with the scary realities of war and violence. Nowadays, school shootings are an all-too-common and horrifying experience, and I'm quite certain that I'll never be comfortable with toy guns in the house.
Likelihood That It'll Last (on a Scale of 1-10): 7 — While I'm pretty adamant about holding my ground about this (seriously, perhaps more so than anything else on this list), my husband has fond memories of playing with G.I. Joe as a kid. Our next-door neighbors (and my little boy's idols) are big on the plastic artillery, too. I'm going to try to stand strong on this, but I'm aware of the reality of outside influences.
Source: Flickr user Lonnie Duncan III