Programming a computer to perfectly counter a human player is hard.
It's why game design - and game coding - is such an art, because it requires countless small tweaks in order to create enemy or friendly AI that's just right.
In fact, it's such a hard craft that good and bad games alike can have flaws in their AI design. These range from small problems that create loopholes for savvy players, to massive issues that leave you wondering why they weren't fixed.
Because, while you can ignore many mistakes in a game, watching your robot teammate continuously walk into a wall - or watching an enemy end themselves - is pretty impossible to forget. Such is the double-edged sword of a broken AI; because it makes you remember a part of the game forever, but for all the wrong reasons.
That said, sometimes having a funny exploit can add a new layer of interest to an old or otherwise ignored game, so it's not all bad news. After all, seeing mistakes only makes you appreciate all the stuff done right even more - so in a bizarre way, it's actually important that they exist.
10. Aliens: Colonial Marines
When the long-anticipated Aliens: Colonial Marines was released in 2013, players found themselves surprised at the, erm, "experience" it contained. Despite the fact that production had taken longer than expected, the titular aliens were about as unnerving as a kitten in a silly costume - and about as deadly to boot.
The spooky extraterrestrials would aimlessly wander about in circles, and seemed to care very little if they saw you or not, instead pottering about like your nan at a particularly exciting bake sale.
Turns out, this was down to an error so simple it's almost heartbreaking: there was a typo in the xenomorphs coding. Fixing said typo in the game's script made the peaceful critters suddenly was more aggressive, and way more bloodthirsty.
As much as this is hilarious, when you think of the countless painstaking hours the production team but in to be sabotaged by a small typo, you can't help but empathise with their suffering.