For apple (IOS/OSX) then objective C or maybe Ruby or lua
Embedded programming then C
Microsoft you have a large choice C# or VB.Net perhaps
Android is Java
Enterprise programming then Java or C#
Pose value haskell or scala :-)
It depends on your background and what you want to do. I think every developer should know C or C++ but not as a starter unless you like serious hacking. Javascript is the language of the web browser so you'd need to know that for any browser programming. Enterprises run on C# or Java.
Then of course there are all the scripting languages python is perhaps the most popular for general scripting, or powershell for windows
Those languages cover many genres of programs: Scientific, parallel/concurrent, server-side, client-side, desktop, mobile, embedded, scripting, business, gaming, and so on.
The question is what are you most interested in? Are you trying to find a job or are you learning because you find it interesting? Do you have projects in mind? What would be the right tool for the job?