Hi,
I want to live extreme sensations around the world and I search for that some activities/attractions unique in world.
I ever saw the aeroplume (flying with an hélium balloon in a cave), surfing on a volcans in Honduras, sleeping in an ice hotel in Kemi, Finland, swimming with jellyfish in a Palau lake...
I want to make a list of these unique experiences in nature.
Have you ideas or examples to complete my list ?
Diving the Blue Hole in Belize - but you have to be able to scuba dive to do that.
Surfing where they are doing it in the Olympics right now
Caving (almost anywhere there are caves)
Going over Niagra Falls in a barrel 
Blackwater rafting at Waitomo caves in NZ?
Heli-hiking onto the Franz Josef and Fox glaciers in NZ, involving going into the ice caves.
Maybe the boat trip onto the Jokulsarlon glacier lagoon in Iceland is a bit sedate?
Sadly visits to White Island volcano in NZ have stopped.
NZ and in particular Queenstown has set itself up as an adrenalin capital, with activities like Fly By Wire which is kind of a zipwire in a hangliding harness as you go down a canyon, and of course it's the home of bungee jumps and jetboat rides.
The main NZ operator, AJ Hackett, used to have operations elsewhere too such as jumping off the Macao tower.
Whitewater rafting in Colorado
Heli-skiing?
Dipping in hole in the ice, popular winter "sport" in Finland. They also do free diving from hole to hole and have competitions.
Cage diving with great white sharks?
If you can do some longer events than this, then it's really up to your interest. You can go on long kayaking, hiking, cycling trips in any number of places around the world with itineraries that suit you the best.
One hike that caught my attention recently was the Alpe Adria Trail <- blog entry by IvaS . You'll need a few weeks to complete the journey though. There are plenty of other cool trails around the world of course.
Hiking active volcanoes in Kamchatka, including Mutnovsky and Tolbachik. This remains one of my top adventures in 51 years of travel.