Good Bad Bugs/Video Games/Survival Horror

Examples of in  games include:


 * Left 4 Dead has a few bugs with destructible environments, especially on Versus Mode. One bug in particular that helps the Survivors is that some terrain and doors are marked 'destructible' so that Enemy Tanks can smash straight through them in order to chase the Survivors through the map. One of these doors is positioned so that once you have gone through a long and painful section of the map, you can flip a switch to open the door to let any lagging or injured survivors into the building without having to run that section of the map. However, because it is marked 'destructible', with enough firepower you can blow the door open and skip that area entirely. This is good for the Survivors, but in Versus mode, bad for the Infected, because it lessens the amount of time you have to eat the Survivors.
 * Fixed in a recent patch along with many other memorable glitches. On the upside, in Versus the Infected got a status bar!
 * This exploit came back when No Mercy was ported to Left 4 Dead 2, but made tons easier since the said door in question could instantly break from any melee weapon used on it. It took valve at least three to five patches to finally plug the exploit, which Valve wrote in the release notes regarding the issue to say "Fixed the fix of the fix of the fix of the door exploit in No Mercy"
 * While the door was fixed, it can still be broken by shooting it with a Grenade Launcher. This bug is not a problem in VS mode since the weapon does not spawn until at least after the event and VS mode does not let players carry weapons and items from the previous map (everyone starts off fresh).
 * Let's not forget some of the other classic bugs, like hanging over non-lethal drops, ability to die while in spawn mode as an Infected, ability to kill yourself by crouch-jumping at odd angles as a Survivor, bots that can help you up from halfway across the room, AI director spawning infected in sight of the Survivors (it's not supposed to), SPIDERTANK, etc.
 * Most of the levels have locations that the infected can't reach, even though they physically can climb up (such as the famous Jesus Rock trick in the finale of Death Toll) or being in certain spots in the finale somehow causes the Tank to glitch out and just suicide almost instantly.
 * There was also a brief bug in "No Mercy" where, if a player threw an item at another player in the elevator, they would plummet through the floor to the bottom of the elevator shaft. Another bug which had a significant effect on gameplay was that player-controlled Boomers could use the suicide command to explode whenever they wanted, meaning that survivors could not push them away without being sprayed.
 * The bot AI also has its shining moments of idiocy: For example, try hanging on a balcony that's just out of the bots' reach and watch as they heroically leap over the edge to their deaths. Sure, you'll have to restart the map, but it's worth it just to see it happen.
 * The TAAAAAAAAAAANK Mutation in Left 4 Dead 2 was a VS mode in which all the Infected players spawn Tanks, all the time. The bug appeared when playing Dead Center. At some points in the first map, there aren't enough places for a Tank to spawn both out of sight of the Survivors and close enough to actually attack them. This lead to Tanks spawning in places outside the building, in mid air, 30 stories up, and falling to their instant deaths.
 * In Clive Barker's Undying, many of the grunts were coded to say a quote as they entered the room where they attacked you but the game had apparently no provision for dealing with a situation where the player killed him before he could speak. This can lead to a situation where you slice off the head of one of the nomadic grunts and his severed head at your feet, looking at you, says "I'll see you in hell!"
 * Silent Hill has a bug where using the bottle of aglaophotis on one of the Stalker Larvae at the Lake Side Amusement Park skips the confrontation with Cybil and goes straight to the (graphically glitched but otherwise unimpaired) cutscene where the parasite is removed. Its handiness in aiding attempts at ten-star ranks and speed runs has made it well-known amongst fans.
 * In the second game, there's a mini-glitch during James's battle with Eddie, where he seems unable to move or attack, allowing James to easily destroy him.
 * In the remake of Resident Evil, you can perform a grenade launcher glitch that allows you to get a infinite number of grenades. Two types of ammo and an item box is needed.
 * This trick does not work in the PAL version.
 * Resident Evil 4 had a couple that were Boring but Practical such as running at 1.5 times his normal speed by switching to the Striker, raising it and then quickly equipping another weapon before the laser sight could activate (useful but cautiously used in speedrunning). However, the most memmorable is Ashley's abilty to suplex enemies by whacking them with a door.
 * Resident Evil 5 had a glitch where you could load guns using the inventory... even if they were the gun you had out. In multiplayer, this allowed skilled players to reload near instantly, circumventing the weakness of many weapons and making chaining combos together a lot easier.
 * STALKER: Shadow of Chernobyl, a notoriously buggy game, had some good glitches:
 * The game world is littered with anomalies that cause damage to the player. The player can get artifacts that increase damage resistance. Once you have the rare artifacts necessary to bring damage resistance over 100%... the once-hurtful anomalies not only heal you, but repair your armour. With no way to repair quickly-degrading objects in the vanilla game... hell yeah.
 * At some point in development, the devs decided to remove vehicles from the game. Installing mods can restore the driving feature though. Anomalies that usually pick up the player and turn them into mush affect vehicles differently; they toss the cars through the air, sometimes at great heights and distances, over buildings etc.
 * In Call of Pripyat, a character named Crab is scripted to stay laying in a bed on the Skadovsk. Sometimes when you load a game where you saved on the Sakdovsk, Crab can be found out of bed. He then starts living up to his name. It's as hysterical as it is terrifying.
 * Dead Space has a glitch that sometimes causes necromorphs to endlessly run around in circles, making them invincible until you block their path.
 * Dead Island has the weapon duplication glitch, which makes a copy of your currently-equipped weapon. This allows you to use your most powerful weapon alone, as well as throw them away when they break, skipping maintenance benches completely. Not only that, you can also earn essentially infinite money by selling a pile of duped weapons.