Might not take out schools with kids, that's uncool. More like poison water reservoirs, trash the electrical grid in 1000's of places. Train track sabotage is also rather easy. There are so many places in the US where a sniper could do so much damage while staying securely under cover - think semi-remote highways, etc. And once we start playing with small drones in urban areas, there's all sorts of creative damage we can cause.