Skateboarding, but I'd be a sad sight. a 30-something bloke on a skateboard.
I see a lot of those around in my neighbourhood. It's okay man, a 30 something on a long board isn't weird. It's cool. Plus, Tony Hawk is about to go into his fifties if I remember correctly... :P
I have never stood on a longboard or a skateboard in my life. So, it'd still be a sad sight. :)
If you know any, ask some young kids to teach you they will love it and you wont have to be embarrassed because kids are cool that way .