Ask HN: Best tool for (several) jobs

I'm a PHP developer by day. I like PHP, I'm good at it and have a decent track record to point to for employers (my first e-commerce site is still going strong 11 years later - though I do NOT want to look at the code :). However, that's really not enough these days. I've been rejected for some recent PHP jobs for people who had also done stuff in Rails - and it's becoming harder and harder to find standard employment with a history in PHP alone (C & Perl don't count for much either as it happens).

So, rather than bitch about how they failt to see my obvious greatness, I'm gonna try and pick up (in a rudimentary sense), a couple of new languages over the next months and build a simple web app with each. I obviously don't expect to become great, but I hope this will at least give me something to show to employers.

This is where I'm stuck. I don't want to just write a blogging platform over & over again - I'd rather build something that the language in question is best suited for. I've bought myself a VPS, I just need an idea of what to build. Relevant communities are always good, but generally tend to be of the "you can do ANYTHING!" mindset and I'm sure that's true, but some languages excel in certain areas and I would like to pursue this.

My plan is for the following:

* Rails

* Python

* Node.js

and possibly some wildcard, which I am open to suggestions for.

I hope this post makes sense and finds you well!