Also include Scripting languages ( Which I couldn't put into the title because it was too long ( Which I just learned AFTER typing all and had to re-write all this ( FUUUUUUU-) and it was still too long ( But I copied my post that time ( >:D) ) ) I'll say JavaScript, for reasons I don't want to retype now ( See above ) I'll learn C one day
NOTE: No bashing other's favorites and [...] PLEASE!
C/++ for sure. Has everything, low level and high level functionality. Nearly everything that can be done on a computer, can be done in C. The syntax makes sense and allows flexibility in styling.