I just love code-golf, I only started recently, but sometimes it's nice to fuck all coding conventions, missuse lazy evaluation and abuse scope leaking.
I'm normally really tidy with formating and whitespace placement, but code-golf is also a testing field for uncommen constructs and I think it can give deeper insights into a language.

I don't like languages specifically for code-golf though, these are just stupid and no fun (at least for me).