If you have downloaded the expansion pack, "The Secret Armory of General Knoxx", then you can travel to Tartarus Junction.

Once there, go down to the area where the small shacks are suspended below the town. Behind one of them is a chest with some guns/mods in it. Take those.

Also, get up on the square vents, then jump to the house with the silver gun case. Take those too.

Then, avoiding the area to the left of the top of the hill, go to the very top area. I use the elevator usually.

On the farthest side, there is a boat hanging down. Jump down into it and grab all the loot there.

Jump off (killing yourself, sorry) then run to the weapon shop.

Sell, save, load, repeat. Happy Vault Hunting.