In a gun-type bomb, Uranium-235 is the fuel. In an implosion bomb, Plutonium-239 is the fuel. A fusion-boosted atomic bomb uses the implosion design, with the addition of gaseous tritium (Hydrogen-3). Producing the appropriate amounts of fuel for bombs is expensive, time-consuming, and difficult.
What does an inhibitor switch do? An inhibitor switch basically tells your vehicle whether its in motion or in park. It can tell the car to park or to go into first gear etc.
The others have covered the obvious symptoms, I'll tell you about one or two that might not be quite so obvious. In many modern vehicles, the neutral switch is integral with a PRNDL switch that illuminates lights on your dashboard to tell you what position your shifter is in. I know from experience that these silly things can get rusty or otherwise start to fail, and when they do you get several symptoms: