I've been playing through a lot of Yu-Gi-Oh games recently. The AI in those games were....strange. Very strange.
Forbidden Memories on the PS1, probably my favorite one. You can't beat the game without either a equip, trap or destruction magic cards. And you need at least 2 (possibly 3).
I farmed 3 Meteor B. Dragon cards (strangest card YOU can get) and couldn't beat it until I memory card traded 3 Raigekis. Trying to win equip cards is EXTREMELY tedious as you need to grind S-Tech victories (having your opponent run out of cards). One of these duels alone can take 20 minutes and it can be expected that you need to do 30+ of them to win the equip card. This is so very time consuming. Same goes for farming trap cards.
The annoying part is that you absolutely need at least more than 1 of these as your opponent can use Blue Eyes Ultimate Dragons which can only be beat my a magic, trap or powered up equip monster.
The AI freaks out constantly, I've had it attack my Meteor B.Dragons with weaker monsters and kill themselves. They've also left monsters in attack mode when I have strong monsters out and on the rare occasion they would just end their turn instead of killing me. These are usually very strong monster but weaker than Meteor B. Dragon. This card seems to make them do weird things.
Not to mention the game just barely followed the actual card system.
Dawn of Destiny on the original Xbox actually followed the card combat system but the AI was weird in that too. Like in Forbidden Memories, they will ALWAYS know the attack/defence of face down cards. So it's pointless trying to play out a face down defence strategy of them attacking you and losing life points. They will almost always mess up cards like Destiny Board by playing the first card then throwing down loads of face down magic or equip cards next to it rendering it useless.
Yami Bakura has Dark Necrofear in his deck which he never seems to want to summon, even when given the chance. Someone told me they once left a whole duel go trying to get him to summon it, he never does.
World Championship Tournament 2004 on the GBA shares a lot of similarities with Dawn of Destiny as it was released shortly after it. The AI generally plays the same too. It's cheap as hell though. Yugi has a maximum luck factor in that game which means he will almost always draw the required cards to counter what you have done. Finally summoned a strong monster? Well it's about to get destroyed my a magic/trap card. So god damn annoying.
Anyway, sorry about the spiel. I could go on and on. I've been on a Yu-Gi-Oh binge lately. The AI in these games really do amaze me.