1. potassium chloride, stops the heart.
2. Thallium poisoning works pretty well.
3. Ricin causes respiratory and organ failure, followed by death within hours
4. Sarin is one of the deadliest nerve gases, hundreds of times more toxic than cyanide. Just one whiff and you’ll foam at the mouth, fall into a coma, and die.
5. Strychnine, Every muscle in your body spasms violently until you die from exhaustion.
6. Mercury, inhaled mercury vapor attacks the brain and lungs, shutting down the central nervous system
Posting this because I don't want to forget it!