This one is not so much an application as a simple shell script. Given the time of year though, snow.sh is fun to watch.
Its big brother, snow.py, does much the same thing, but uses a range of characters that actually look like snow.
Visually an improvement, but I should mention that if I try to use snow.py on my framebuffer machine, I get a flurry of … inverted question marks. 😀
Before you dismiss this as a three-second diversion, consider including it in screen‘s blanker options, as your terminal screensaver for winter moods. According to your hemisphere, of course. … 😐