If you are referring to the knife trend in the UK, it is ILLEGAL, kids in gangs on bad estates have them anyway. Obviously they'd love to have guns like in the USA, but fortunately it's simply not available to them. Thank goodness for that I say.  The police confiscate these knives at every opportunity and regular kids certainly don't have them. It's illegal to buy dangerous knives, so such knives are home made.  

Still, the average person cannot do anywhere near as much damage with a knife as they can with a gun.