Kiki Challenge
This challenge had people step out of a moving car and dance along to the beats of Drake song. Many people took it to roads and got out of their cars to record which even lead to road accidents.
Fire Challenge
Yes, it is exactly what it sounds like. People poured flammable liquids on themselves and lit them on fire.
Salt and ice challenge
People put salt on their skin and topped it with ice to see who could handle the pain. This clearly ended up in burns for them.
Helium voice change
This is not a recent discovery but many people have tried temporarily changing their voice by inhaling helium. This in fact, is very dangerous and can also cause your lungs to collapse.
Nitrous gas inhalation
Commonly used by dentists for treatments, nitrous oxide when inhaled can make you giggly. Some people use it as a joke without being aware of the consequences. Please do not consume it under any unsupervised environment.