In most game AI ( 3D shooters ) the entities have to have a degree of randomness, as their default weapons programming gives them perfect aim.

It's imposable to get perfect humanistic AI, as there are millions of factors that make us "unique" in our behavior.

One time I tried to write a "code cracking" algorithm that would try every single permutation of the alphabet to break a code.

Basically, it was a challenge between my friends and family to create our own glyph alphabets and use it to write a coded message. Then we had to try to crack each others codes. I knew they were going to take the simple approach of just using glyphs to substitute letters of the alphabet. So to remove the layer of crypticness of their alphabetic glyphs I knew I could just substitute a letter of the English alphabet for each of their glyphs. That would turn it into a scrambled alphabet code rather than a glyphic code. When I realized that, the programmer's gears in my head started turning... I knew that, theoretically, their codes could all be broken by a computer program that permutated combinations of the alphabet and attempted to recognize the correct key when it could identify common words like "the", "and", "a", "is", etc consistently throughout the document. So I wrote the program to do it, and let it start hacking away at the codes with its brute-force approach. Meanwhile, I worked on solving the puzzle by brain-power.

To make a long story short the human brain broke the codes within an hour or two. Two days later, the permutation algorithm STILL had not broken any of the codes lol. There's just WAY too many permutations of the alphabet! After all, that's 26 different letters that can be arranged in a huge number of orders (I forget the exact number of permutations). So I killed the program and shelved the idea, though it was an intersting learning experience. :-)