I have been thinking about this since I read about the guy getting knifed on a DC Metro. Actually, I have thought about it since before then but I have become more serious about it since that happened. Then, during another thread on this site someone brought up self-defense when in places where law abiding citizens are denied their Second Amendment rights and I thought this would be a good place to discuss this.

What are some good weapons of opportunity that are found almost anywhere? So, since the guy was knifed on the Metro I have looked around and I know where the emergency stop switches are in the cars (thinking this could throw the guy off balance) and I know where the fire extinguishers are (enabling me to shoot the extinguishing agent at the threat to momentarily blind/choke them, and then use the extinguisher as a club).

What are some other things that are commonly found that can be used to defend yourself and others if attacked?