That I've witnessed, seeing a guy getting tasered. From what I could tell, his wife was trying to take his children out of the country (I guess he was abusive or something because the wife had a police escort and I guess had a restraining order against him). Anyway we were in the airport and she was getting rushed into the building by the police, but 30 seconds later this guy turned up sprinting after her, and one of the children (he was about 2 or 3 years old) starting running towards him. More police arrived and stopped him, but he was Polish and clearly didn't speak a word of English, so their attempts to calm him down just made him panic, and he took a swing at one of the policemen, and then another policeman came out of nowhere and tasered him right in the chest, and just stood there, meanwhile the child was next to him screaming, the guy was rolling around on the ground getting electrocuted, and the police were shouting at everyone to put away their phones... total chaos, I was worried they were going to kill him (there was actually a very similar case a few years back where a Polish guy who didn't speak English was detained in an airport, and lashed out, and he was so panicked that they kept tasering him until he passed out and he never woke up.)
Scary stuff, made me lose a lot of respect for the police because whatever he had done they clearly had made no attempt to handle the situation properly, they didn't have a translator or anything. (although its also a good argument for making sure immigrants learn the language, when something extreme like that happens I think we'd all resort to violence if we had no other way of communicating and the police were effectively stealing our children).