Well spoiler tag it, or if it's really bad PM me coz I'm burning with curiosity now XD
For me, it'd be free diving. Nothing I can think of compares when you're in a good bit of water. Sunlight arcing through the water, fish/coral everywhere, visibility good for ages and ages, water warm but not too warm so it's still refreshing.
You tried skiing/snowboarding ? That was pretty epic i guess.. getting up at 7am, above the clouds in beautiful sunlight being one of the first down the top of the mountain, with untouched crisp snow, feels epic.