From torture, to mind-control projects, to hiring hookers to rape men, to dumping viruses and bacteria on cities, to injecting people with plutonium and infecting people with siphilis just to watch them die... The U.S. Government, ever since partnering with Nazi War Criminals at the close of WWII has carried out dozens of completely illegal and unethical experiments on humans. The U.S. Government currently has about 1,000,000 people with top secret clearance working domestically in the United States - that is twice as many per capita as Nazi Germany had S.S. officers. People who care about integrity, honesty, ethics, and goodness will steer clear of these criminals - resist them even. If someone approaches you to help them as a confidential informant or otherwise, refuse.
http://en.wikipedia.org/wiki/Unethical_human_experimentation_in_the_United_States
http://wariscrime.com/new/the-13-most-evil-us-government-human-experiments/