Lots of fun stuff you can program in Minecraft Pi Edition. My son and I made a minecraft version of snake/tron where each player would leave behind a trail of TNT blocks as they ran around a closed arena. Hitting a TNT would set off such huge chain reaction of explosions that the raspberry pi couldn't handle it. After a few rounds of these explosions the minecraft world looks like a total wasteland.
I honestly wish they had some of that level of scripting for the desktop version too, I love the idea of doing Python with Minecraft. Plus fun ideas like that could scale a little better on a much more powered system.
There is a custom plugin/language to extend vanilla Minecraft server transparently called Denizen. Custom yaml based scripts and even repl in-game