Zetroxin
Zetroxin is an odorless, tasteless grayish gas that is supposed to be 80% fatal. There were supposed to be no other side effects. What was not known was that 75% of those who did not die from contact would have a psychological break. They then become ferocious killing machines. (Think 28 days later here)
The United States used it against the WAIS in an effort to contain the rebellion. The United Nations banned it's use in 2028.
