I'd have to agree to the Japanese Ohka rocket bomb. Technically, if the Japanese had developed a guidance and launch system for it, it could've been a precursor to the cruise missile.
Unfortunately, having it carried by a very vulnerable Betty bomber on the way to the target makes the weapon system very vulnerable to Navy CAP.

As for the neutron bomb, I tend to think that there is a certain logic to it. It was an attempt to make a "clean" nuclear weapon. It's a disgusting thought but that's how I see it.