What hobbies, skills, or knowledge would you pursue if you had forever to master them

I'd like to do some dangerous sports.  I used to be timid but if I couldn't die, I would do these things as I please. 

Welp, the risk of these sports may be their core. In part it's interesting because of their danger and risks. So I might not enjoy them any more... 

It was really hard to live as an immortal...