Unless you're planning on going into enterprise software development, I'd argue that the similarities between Java and C++ are sufficient enough to ditch one of

Unless you're planning on going into enterprise software development, I'd argue that the similarities between Java and C++ are sufficient enough to ditch one of the two (at least in terms of fundamentals). You could also substitute Java for C sharp, if you're so inclined, or Python for Ruby. I'd definitely switch Perl for a decent shell (and sed and awk). I know it's not fashionable here but I'd probably bail on Lisp. While it's a great language it's not that widely used and you'll either pine for lispness in other languages or you may well hate it like I did (although I do recognise it's power, I was spoilt with python). Ultimately though, the hacker skillset isn't a skillset at all, it's a mindset. It's the ability to bend the world to your will. The ability to say, "There are no rules and there are no limits that are not self-imposed". That for me defines the difference between regular people and hackers.