Tear gas is a non-lethal chemical weapon often used in riot control to disperse aggressive protestors. When released from thrown canisters, the resulting cloud can cause great irritation to eyes and lungs, leading to itchiness, coughing and temporary blindness.
The weapon was first seen in Sonic the Comic Online, used by a paramilitary group led by Captain Blue and Mr Gold. The gas was utlilised during a peace rally, supposedly fired upon scared people proposing talks with Doctor Robotnik. The tear gas incapacitated the peaceful protestors enough for Gold's men to "arrest" anyone they could catch. The attack greatly annoyed Amy Rose, with Tails also being a secondary witness through "tapes".