Help the man in the falling down building towards the south of the Hub marketplace. Once the raiders are dead, he gives you the .233 pistol, one of the best pistol in the game.
Access lockers and get The Blades' weapons and ammo
Go to the place above the cathedral, LA Downtown. Go to The Blades' leader. Tell her that you will get the weapons that she needs. Fight your way past any Deathclaws and go to the Gun Runners. Get good weapons and talk to Gabriel. Offer to take care of all the Deathclaws, and he will present you with two options -- either get lots of weapons and ammunition for yourself, or give weapons and ammo to The Blades. At this time, choose the answer for yourself. Take care of all the Deathclaws, including the mother and her eggs. After this, go back to Gabriel and tell him you have taken care of all the Deathclaws. Take the weapons and ammo for yourself. All the people should move around. Walk off the stage to the place where the Deathclaws were, then walk back. Everyone will stop moving. Talk to Gabriel. Ask why he does not get many visitors, then tell him that you killed all the Deathclaws. He should say that you have to wait a few days. Return to The Blades' base and rest for two days. Go back and he should ask you what you want for killing all the Deathclaws. Say that you have some friends who could use weapons and ammo. If done correctly, you should be able to access the lockers but still get The Blades' their weapons and ammo.
Alternate desktop icon
Create a shortcut to the game on the Windows 95/98 desktop. Then, use the Settings/Control Panel/Display/Effects options to turn on "Large icons". The desktop icon for the game will turn into a new graphic.
Bartering
Create a character with good barter skills, and upgrade them whenever you level up. When bartering with someone, you can easily trade back and forth the same item. Empty them of all their items if you desire, leaving them with 1 cap. This works with everyone with a lower barter skill than you. The best person to do this with is the dwarven man with the gunrunners, especially considering the "Weight glitch". Basically, you can say to someone: "Swap my stimpak for your identical stimpak and all your money." It takes a while, but you can leave the gunrunner trader with just his (regenerating) caps, and keep swapping items around to get more.
Better armor class
Note: This trick requires v1.0 of the game. Get a bag and some armor. Equip the armor, then enter the bag. Drop the armor off of your character, then pick it up. Repeat to build your armor class.
Credit comments
Hold [Shift] during the credit sequence to hear comments from the development team.
Crossing to the gun runners base
Once you have the Advanced Power Armor (getting it as soon as you are in the Brotherhood is recommended), you can easily walk over the narrow section of sludge around the gun runners base.
Exploding developer
Type boom at the credits screen to see an animation of producer Tim Cain's head exploding.
Fast caps
Go to the casino/bar, talk to the black man wearing metal armor and hold 1 + 4. In about a minute you will have over 2,000 caps. You must have at least 55% on Gambling to get this amount. The higher the percentage, the faster you will get more money.
Good conversation results
If there is a chance that a conversation may randomly not go too well (for example, if the roll against your Speech skill fails), simply save before talking to the person and keep going until the conversation goes favorably. This also works well when you are lockpicking or detecting traps on something tricky.
Gun classifications
Small guns covers rifles and machine guns, not just pistols. Big guns only covers minigun, flamethrower, and rocket launcher size weapons.
Mutant vat torture
Bring an NPC through the mutant vats from the watershed mutant in Necropolis. Load him up with your weapons, armor, stimpacks (save 5-10 in your inventory), and ammo, but do not bring everything. When Harry takes you to the vats and the torture begins, use the stimpacks in inventory to heal in between the torture sessions. Take your items back from the NPC after returning to your room.
Plastic explosives
Plant a plastic explosive on someone, then click on your pip boy. Click on the little bell and rest for one or two hour. When the plastic explosive blows up, all their items will be on the floor, but you will not go in combat mode and the person will still be alive.
Red Ryder BB gun
When you encounter Bob (who sells cars), kill him, then go inside his house. You will find a crate with a Red Ryder BB gun. The BBs can be found in the footlocker (which you will have to pick the lock).
The Glow
The glow is not as bad as people say. You can go there very easily just by dosing yourself with Radx, and taking Radaway when you leave. Be sure not to do too many things that take game time (play chess with the computer, use skills, etc.). Look out for the keycards, and remember each lift is trapped. You can get some valuable weapons and even more valuable information. It is a good idea to go straight to the Brotherhood, then straight here after the water chip is found.
Weight
Your character can hold infinitely more than his maximum carry weight by trading with someone. The game doesn't check to see if you can carry what you are buying. For example, a character can have the minigun, the flame thrower, rocket launcher, plasma rifle, .233 pistol, as well as lots of heavy ammo. If you have a problem where you need to pick something up from the game world, you can give everything except your money and other light things to Ian, then pick up the item. You can get all your items back, thanks to both the "Barter" and "Weight" glitches. Unfortunately the NPC fails to realize that the items are yours and that you just gave them to him to hold.