For me, the most fun can be had with ActionScript 3.
I love the syntax, tools and community behind this language. The structure can be clean (as long as the developer follows OOP best practices) and its footprint low (as long as the developer follows OOP best practices). The only issue I have with the language is how easy it is to write lazy code.
If anything, I think AS3 needs more structure. More rules need to be set for better produced apps. There needs to be more penalty for allowing code writing that may induce memory leaks. For instance, with Xcode 4 and a C-based language, it checks as you type for the possibility of a memory leak and then notifies you before the compile. You don't even need to run your application to see that there might be a problem. Of course, that's more the feature of the newest compilers included with the iOS/OS X SDK, not the language itself.
Another bit of beef I have with AS3 is the fact semicolons aren't required at the end of lines. I'm not Christopher Walken reading a script. I need to have punctuation. Endline characters are like a period at the end of a sentence. Programming in AS3 should follow some kind of grammar standard, but I guess that is my OCD shining through.
Even with those little complaints about the language, it is still my favorite environment to develop in. It just does so much! But who knows, Objective-C/Cocoa might take that crown soon.
My favorite programming language is currently Ruby. Three years ago I would have said Java and before that I might have said C++. I even spent a few months infatuated with Python, but it was short lived. Right now it is Ruby. It has the prettiest syntax. Reading through Ruby code makes me happy. It is simple and elegant while still being powerful. The community that surrounds Ruby is passionate and is always releasing new tools. With every language that I have learned it has taught me a new perspective and approach for working with code. I assume that some day some other language will sweep me off my feet and become my new favorite. Until then I will enjoy working with Ruby.
I struggled for a while with this one, but the more I thought about it and as we discussed it in the office, CSS is most definitely a programming language––and it's for sure my favorite. CSS is pretty powerful and it's becoming even more powerful with things like media queries, position and number-based pseudo class selectors, and content-related pseudo elements. I love the way it's structured and I love organizing a site's stylesheet in the most efficient and flexible way possible. I really enjoy writing CSS and the possibilities get me all excited.