1.A crowd
Rioters, looters, a mob.
The collective noun for people in a riot is a mob of people.
The angry crowd began to riot when the police attempted to make them disperse.
You can't get a gold riot shield in Call of Duty: Modern Warfare 3.
They called it the "Boston Riot".
No, you cannot shoot whilst holding a riot shield.
Estimates suggest that around 200 people died in the Kano riot of 1953. The riot was a result of political and ethnic tensions in Nigeria at that time.
No. That would be outrageous. I would call for a riot.
strike or riot
In Call of Duty, no, but in real life you could, but only if you could hold a gun and a riot shield at the same time.
Animals in large groups have really interesting names. For example, a group of crows is called a murder, and a group of rhinos is called a crash. Kangaroos are commonly known as a mob, but some people call them a riot.