I’ll follow Dave Ray and will try to say something nice about a bunch of programming languages I use or have used seriously:

Ada – The only language I would trust my life to.

C – It gets things done easily in a controlled space when resources are scarce. I use it in many embedded situations, often with FreeRTOS.

C++ – Its templating system with specialization beats everything I know. When I worked on Urbi at Gostai, I had a lot of pleasure using it.

Erlang – The language to use to develop distributable parallel applications. I wrote many programs for research projects with it.

Factor – One of the languages I feel the most comfortable with. I really like the reverse polish notation and the powerful combinators. I use it for many personal and teaching projects.

Forth – Forth is one of the languages that I have been liking since the first time I heard about it. Its conciseness, simplicity, grammar and ease of implementation beats almost everything when it comes to size on very small embedded systems. I used it to write a Forth compiler targetting the Microchip PIC16Fxxx microcontrollers family.

Haskell – I started using it when I had to send patches for Darcs. I really love monads, and I also love explaining them in class. My window manager configuration is also written in Haskell.

J – It is unbeatable if you have RSI and need to type as little characters as possible for a task that can be applied to a whole array. I use it mostly to solve Project Euler problems.

Java – Well, everyone knows it so it may be used to explain a simple concept. Is that nice enough?

Javascript – Javascript lets us do things in the browser I would not have imagined five years ago. For example, this web page is static but includes Twitter updates and comments, thanks to Javascript. On the server side, I use it within a CouchDB database where I store a whole web application; it dynamically generates iCalendar views for multiple people from data gathered at TVrage.com using their XML API.

Python – I can hack anything in a few minutes and still be able to read it later. I wrote a Forth compiler for the Microchip PIC18Fxxx microcontrollers family with it.

Ruby – Feels like Python, only more functional and cleaner. I would use it more if I had not been bitten by threading unstability on Sparc64Linux in the past (for the will-spam-for-food.eu.org service we ran with Pierre Beyssac and Thomas Quinot). Ruby helps me run this blog.