Kind of surprised no one mention gambling yet.
At any rate, a safer bet is to join Elven Blood on Facebook and duel miscellaneous strangers.
Wear a fur coat to a Greenpeace meeting.
Psst! See Post #1!
Why does this make me think of Kentucky Fried Movie’s, Rex Kramer: Danger Seeker (it’s on YouTube)?
Oooo! Ooooo! I know! Gambling.
I would suggest stringing a wire between two of your neighbor’s houses, and attempting to wire walk the distance. It’s risky legally (trespassing), socially (perhaps not terribly risky in and of itself, unless you do it in the nude – for a real risk, try nude wirewalking while masturbating…that might be socially risky enough for you), and finally, financially, because you could be sued for trespassing, or lose your assets when they incarcerate you against your will for being mentally and/or emotionally unstable.
Another idea is to write a threatening letter to the president.
Audition for American Idol while drunk.
Legally, socially, and financially risky? Shoplifting.
Call people on their bullshit.
Parkour?