You know one, you know them all, at least with the oo languages.
If you are seriously into programming you can't go without C/C++.
Assembler (Assembly) is not needed anymore in most cases, unless you work very close to undocumented hardware (no os api).
I am actually working more with Java myself, but that is only because university forces me to (practial exercises/experiments). It is quite a strong language but is based on a very inefficient VM.
Python gives a lot of options to skilled programmers, since it is not a strict langauge, there are some people calling themselves python-jedis and their code works by symbolic hand movements somehow I heard.
It is a nice concept for a clean looking language, though it's open style (no strict types) makes it less efficient than C.
And... not trying to break some peoples illusions, but HTML is no programming language
.