Some time ago, I implemented Langton's Ant in C. Langton's Ant is not more than a very simple Turing machine. However, even with those simple rules, its behaviour is not easy to predict.
I've read about Langton's Ant in an article of Spektrum der Wissenschaft (German) years ago and on one dull evening, I decided to implement it in C. You can download and try for yourself at https://github.com/keisentraut/langtons-ant.
It's nothing new, but I liked implementing it and some nice screenshots are below:
Langton's Ant 10
This one start "building a highway" after a few thousand iterations:
Langton's Ant 100
This one keeps being chaotic:
Langton's Ant 1001
This bitstring results in a semi-chaotic, semi-structured behaviour:
Langton's Ant 1000111010111100011100100100111110111111
I can't really describe what this one does: