Programming - Python
Back in 2007 I moved from exclusively using Windows PCs to using a Mac for several years. The only real problem I found was that I'd previously written a lot of small utility programs, and I wanted a way of quickly recreating them on the Mac. As I still used Windows occasionally, I decided it would be good if any solution would also be cross-platform. Given that the utilities were generally small, and I wanted to be able to recreate them relatively quickly, it was obvious that what I needed was cross-platform scripting language.
There are quite a few of these around, but the one I selected was Python. It seemed to be widely used, widely liked, and a brief scan of some example scripts suggested that it wouldn't be too difficult to learn. Initially I was sceptical of it's much-maligned "white-space is syntactically significant" aspect, but I soon found (and no doubt other Python users will now be nodding their heads sagely) that it was easy to get used to, and soon felt entirely natural. I imagine it helps that in all my programming I've always tended to be a stickler for consistent indenting.
I have a number of Python projects on Github at the moment, mainly small command-line utilities as Python excels at these.