I've been using Pico-8 for about a year now, and I really enjoy what these "fantasy consoles" have to offer. For making a quick game or visual effect, it does an amazing job.

There are now a number of projects of a similar vein to Pico-8 out there, including this one, but I think this can fill its own niche. To my recollection, this is the first one that I've seen using blocks.