I'm about to do Dead Money on my second character, but I've forgotten if you can bring your good old stim's into it. I just would like to know if you can, because if you can I'mma go buy two hundred :')
The Rad Child and Them's good eating perks makes stimpak hunting less of a hassle.
If you pick Rad Child, be sure to have radiation sickness before you enter (I'll recommend stage 2!), and don't use the auto docs as they cure you of it.
I believe you can also take the missing laser pistol from the unmarked quest you get from Quartermaster Torres at Hidden Valley, oh and the Van Graff armor if you steal it from the footlocker beside the entrance to the Silver Rush. You can also use the multiple companion glitch and whatever they're carrying they keep
There might be more, but there are 4 things I know can't be removed. These things are the Rebreather, the Codac 9000, the Missing Laser pistol and Motorrunner's Helmet.