With programming languages it is often horses for courses but I think it would be fair to say that C# is overall my favourite (and certainly most used) programming language.
I have found that I am only able to be good at 3 languages. This is probably a limitation on my intelligence! I can (and do) faff with more than 3, but I can only say I am "good" at 3 languages and I don't seem to be able to add any more to the "good" list without dropping one that is already on it. So here is what I've settled on:
Computer and Web based applications: C#
Embedded Systems: C
Scripting and fun: perl*
* these days perl has fallen out of favour and python has taken its place. But I have never got on with python so I'll stick to my perl, thanks.
Others that I faff with: elisp, php, javascript, vba