Wired magazine has released a list of the 10 deadliest poisons that work either by ingestion of inhalation. They include:
Cyanide: Cyanide exposure leads to seizures, cardiac arrest, and death within minutes.
Sarin: A deadly nerve gas hundreds of times more toxic than cyanide.
Botulinum: Several orders of magnitude deadlier than sarin, this poison causes your nervous system to fail, resulting in an extremely painful death.
Mercury: Inhaled mercury vapor attacks the brain and lungs, and shuts down the central nervous system. Mercury starts turning into a gas at room temperature.
Compound 1080: This poison is odorless, tasteless, and has no antidote. The bodies of those killed with 1080 remain poisonous for a year.