Best A.I. in old videogames

Final Fantasy Tactics for PSX

Freeze Man's AI is pretty simple. I think the only thing he does is jump whenever he gets shot at.

Having stuff trigger when being shot is common in MM games. Darkman1 does the same thing in MM5, he shots when he gets shot at. Then, some other enemies/bosses are based on which buttons the player presses on his pad.
Try Mr.Gimmick on NES. Basic enemies have better AIs than that.

So I went on a binge making Mega Maker levels, and my favorite robot master was Metal Man. If you get close to him, he jumps over you. If you're far away, he throws things at you. I put him in a room with moving platforms and made his weakness a weapon that works best in close range. The result is he jumps all over the place throwing a million buzzsaw blades and it freaks people out because he acts like he's throwing a tantrum. But I also put a pit in the middle of the room. If you understand he jumps when you get close to him, you can trick him into falling into the pit. People love that kinda thing.

On the one hand, I like Mega Man bosses because they always have some pattern. They're my favorite retro AI. On the other, I feel like any player who's got his ducks in a row should be able to beat a boss on their first try. Of course, he REALLY needs his shit together. What really happens is you fucking die over and over so you can learn the pattern, and once you learn the pattern, bosses are either easy, boring, or trivial.