Back when Java was my favorite language, I was once challenged to spend an hour looking at Objective-C and see if I didn't grok it in that time period, and then a week working with Cocoa-- and was promised that I'd love it if I did.

They were right.

I still believe Objective-C, paired with Cocoa is far and away the best programming language and environment out there. I've worked on the internals of windows, lots of C++, lots of Java (used to be my favorite), done .net, done a bunch of scripting languages, python, perl, lingo and actionscript, and lisp and erlang.

On the server it should be erlang (for serious code, for less serious use your favorite script)... and on desktop and mobile, Objective-C and Cocoa are really quite spectacular.