VX
VX works the same way other nerve agents do.  It blocks nerve signals from getting from the brain to the body.  Normally, a neurotransmitter (chemical messenger) called acetylcholine tells the body's muscles to tighten up when they need to.  When it is time for the muscles to relax, an enzyme called acetylcholinesterase destroys acetylcholine, so the muscles stop getting the signal to relax.