A.I. is absolutely needed for most modern day video games. If you aren't playing against an opponent, then you are probably playing against A.I. bots of some kind. Outside of computer-controlled enemies, games love to saddle you with computer-controlled allies as well. At best, dumb A.I. is a minor annoyance. At worst, it completely ruins the game you are playing. In this list, we don't rate the games based on how bad the A.I. is per se, but rather how much amusement we got out of seeing the A.I. fail. Hopefully you enjoy them as much as we did.
Doom 3 wasn't the easiest game out there, but that certainly wasn't because of its brilliant A.I. In fact, every single enemy without a projectile attack had one important weakness: tables. If you jumped on a table outside of a melee enemy's reach, there was absolutely nothing they could do. They would run around in circles around the table moaning and wailing, easily within your grasp, without ever attacking. Projectile enemies could always shoot you, but melee enemies never thought to just reach above their heads once in a while.
Jump Ultimate Stars was a fun Smash Bros.-style DS game that brings together popular anime characters to slug it out. It was great to play against other people, but the A.I. was so stupid that people would actually recommend that you avoid buying the game if you have no one to play with. The A.I. would repeatedly jump to its death in any stage where they were able to, many times right after a respawn. On top of this, the A.I. actually cheated at high difficulties so that you could barely ever land an attack, but you could still win by waiting at the top of the screen and doing nothing while the A.I. killed itself.
The Uncanny X-Men was made notable by an episode of The Angry Video Game Nerd that focused on its incredibly crappy A.I. Since there was no way to play the game with one character only, single-player mode gave you an A.I. teammate. Unfortunately, this teammate did not necessarily know to follow you when you tried to move forward in a stage, and so you would frequently get stuck as he endlessly ran into walls. It was actually far better to purposefully let you're A.I. teammate get killed so you could play the game freely.
The biggest threat in Fallout was not your enemies, but your own party members. They absolutely loved to shoot you in the back every chance they got. They also loved to trap you in walls and corners to make it impossible to continue on with the game. Strangely enough, this pattern has stayed true even in more recent Fallout releases. Try running in front of your A.I. allies in Fallout 3 and they will shoot you in the back all the same.
Tales of Destiny was one of the first Tales games to ever make it to American shores, but unfortunately, in the early days of Tales, the combat was a little broken. Your A.I. teammates would very frequently do nothing in battle. In fact, to get them to do anything at all, you frequently had to stand behind them so they'd wake up. Since you normally controlled a melee character in the game, this made your A.I. partners pretty much useless.