I asked this over at Goarmy.com forums, and they wouldn't give me a straight answer, so I'll ask it here.

I've read all about all the different gear that different guys recommend taking into a deployment (in addition to army issue) and I was wondering what exactly the army will allow you to take.

I've read all sorts of things that people recommend taking (some of it on the "kit up" articles on this site), from "plasti wrap" to protect a laptop, to a good ol' kabar, to a usb flash drive. I have also talked to people who have said that you can't take a Kabar because thats what the marines use, and you can't carry and M9 because it's not standard issue. Is there a regulation on this someplace, or does it depend on the CO?

Above all I would guess the key items for a day journey would be a rifle, water, knife, etc. But does the Army issue you a knife for instance? Can you carry a leatherman multi-tool? Do you guys even get to carry an M9 bayonet (not that it has a great track record) or can you go buy an M7 to take along instead?

Is there a standard for all this stuff written down someplace?

Most of the theater-prohibited items are listed in the CENTCOM General Orders, which are read to soldiers prior to deploying. It's a long list, but the generally prohibited items are:

1) Personal firearms.

2) Firearms accessories that alter the function of an issued weapon (i.e. collapsible buttstocks for the M16A2/A4, sear conversion kits for full auto, etc.). Optics like an add on scope are generally allowed, but may need to be cleared through the chain of command.

3) Personally purchased body armor.

4) Personally purchased ammunition or explosives.

As for personally purchased equipment, there are alot of things authorized, but you should be prudent as to what you buy. You CAN purchase and carry a multi-tool and a knife, but they are not standard issue, unless you deploy. Deploying soldiers go through RFI (the Rapid Fielding Initiative), and receive all kinds of gear. The M9 bayonet is general issue, but in my experience, no one carries it; it's not very practical on an M-4 carbine.
Alot of new soldiers go out and purchase every high-speed looking piece of gear that they see in the Ranger Joe's catalog, and I would advise against this. Save your money, and buy the occasional extra item based on experience showing that you need it, NOT because it looks cool.