Discovery channel just told how to make nerve gas.  Hope no terrorists were watching.  Heres how you do it (totally serious).  
Step 1: Take some anti-arthritis medicine that consists of DMSO.  Pretty common stuff.  
Step 2:  Breath pure oxygen for a few minutes.  This accelerates the breakdown of the DMSO into DMSO2
Step 3:  Withdraw some blood into a syringe, making sure it cools to room temperature quickly
Step 4:  You now have DMSO4, a deadly nerve gas.
A hospital withdrew some blood from a patient, and the whole ER passed out.  Just the gas that escaped from a syringe was enough to cause permanent damage to many nurses and doctors.