Pancuronium bromide
Because the brain is not a muscle, pancuronium bromide does not paralyze the brain.  This means that pancuronium bromide is not a sedative (it will not put a person to sleep), and it does not kill pain.  If a person is given only pancuronium bromide, their brain will keep working normally even while their body is paralyzed.  They will be awake and aware of what is going on, but unable to move.