The Pitt bugs

Cloning concealed weapons
Before attempting to infiltrate Downtown, have Wernher conceal a gun or knife on you.

After your gear is confiscated by the Pitt slavers, stop moving. If you move too far forward, you'll encounter a guard interrogating three slaves, and the door you were just ambushed at will lock behind you. Go through that door, drop your concealed weapon and ammunition, and then step back through the door. You'll find that a new concealed weapon has spawned on your person. Repeat the process as needed, repeatedly traveling through the door and dropping your weapon until you have cloned a satisfactory amount of that weapon.

As a side effect of the bug, you may find additional copies of your concealed weapon when you retrieve your gear from a locker after winning the Arena fights.

Auto-axe audio problem
It is possible that upon first use of the auto axe the audio will play the sound of the axe being started, constantly repeating throughout use. This sound takes the place of the normal sounds of the axe blades spinning. So far there is no solution to this problem.

Problems retrieving your gear
For some people, if, after the third fight in The Hole, you don't retrieve your gear, then complete all three quests, it is no longer in the footlocker. After the third fight when trying to retrieve your gear it crashes the game

Map marker glitches
Installing The Pitt often causes user-placed map markers to cease functioning correctly in a large area around Megaton, Meresti Trainyard, Agatha's House, the Bethesda Ruins, and Wheaton Armory. The compass visible on the HUD may direct players in the opposite direction of a map marker placed in this area. The compass may also indicate that an affected map marker is a considerable distance away, when the marker may actually only be a few feet from the player.

Other users have noted similar conflicts within the map system, such as areas of the Megaton Local Map wrongfully being marked as unexplored.

Steelyard terrain glitch
Players who have both The Pitt and Point Lookout installed may find that parts of the Steelyard have stopped being solid. Bethesda has confirmed that Point Lookout is the source of the bug, and recommends that players affected by the bug uninstall and reinstall Point Lookout. Many players have been able to temporarily fix the bug just by saving at the edge of the broken terrain, restarting their consoles, and reloading the save. Uninstalling a DLC pack may reset all quest progress within that DLC, and may remove all DLC-specific items from one's inventory and containers; therefore it is best to try the save-reload workaround first.

Bridge terrain glitch
If, at the Bridge, you jump down to the rocks below, start getting irradiated, and then quickly fast-travel back up, the Bridge may become impassable. Somehow, fast traveling in such a manner causes the area to load incorrectly, such that the lethal radiation on the rocks is also applied to the Bridge itself.

Non-player characters go invisible
When you enter the Mill and kill slaves who are working with an auto axe, they suddenly can turn invisible they only turn visible again when you killed them.

Auto axe goes invisible
Under certain circumstances, the auto axe may become invisible in first-person view. This may sometimes occur when killing Pitt slaves in the Mill, or when using the primary fire for the weapon for the first time.

Ashur's speech
Talking to Midea while Ashur gives his speech may break the quest scripts. Ashur will stop talking, the quest will not continue, and the entire game may behave erratically or crash. Walking under the platform that Ashur stands on during the speech can also trigger a crash.

Ashur bug in Haven
When entering Haven and talking to Ashur for a quest objective, Ashur may stop talking mid-conversation, and you will exit the speech box. He will then continuously say, "Don't let me keep you". This will prevent you from speaking to him again, and also trap you in Ashur's home. Reloading a previous save will fix the bug, as will killing Ashur and kidnapping Marie.

Getting out of the map
If you go to the Steelyard you will see a large silo with a walkway attached to it. There appears to be no way to it. If you go up the stairs to the upper levels where the wild men are, you will see a building near the silo that you can't reach. You have to climb to the higher levels to get to it then jump off onto the roof. The fall will probably kill you so when you jump pause the game and save it just before you hit. Then load the save and you will be fine. You will see another building slightly below you. You have to jump onto that and from there you can jump onto the ground right outside the Steelyard. You will now see buildings that are slightly off the ground and a very hilly terrain. You will also see the walkway leading to the top of the silo, for access back into the Steelyard. From here you can walk towards the buildings which are just decorative, so you can walk through them. You will reach a very steep hill that will take some time to get over. Once you do you can walk for a while and see almost nothing except flat ground and a hill that you can't climb. Keep walking, however and you will see what looks like a colorful chasm stopping you from going any further. It's actually a very deep river. If you throw grenades into it they will cause a massive explosion of bluish-light. Eventually you will no longer be shown on the map. Presently there is nothing else of interest and you can presumably walk forever as the longest time walking here in a perfectly straight line was 4 1/2 hours with no edge in sight.

Also outside of the map is a river colored blue, like the water in the Nuka-Cola plant.

Prevent gear stripping
You must take off your gear including ammunition in the Pitt after traveling and store it into the nearest container. Go to Downtown, through Mex. After Mex "takes" your gear, head on up and find the place where you store your gear through fast traveling through the location you stashed your gear. Note: The location must have a marker on the map.

Partially-Invisible Gun
After exiting Haven after kidnapping Marie (a.k.a the cure), if you pull out the Infiltrator while near the northwest corner of the map, the game won't render the barrel of the gun, and will in turn freeze your game.