No, there aren't any cheat codes in the Xbox 360 version of Mass Effect 3.
If you're having trouble with money or combat, you've got several options. At any point you can turn the difficulty down in the options menu if you think the combat is a bit too challenging. Further, the more you explore the galaxy, probe planets and scan systems, the more credits and other items you'll acquire.
If you do this early on in the campaign, you should have plenty of resources and find yourself having an easy time as you continue.
Further, if you download and install the free Kingdoms of Amalur demo, you can unlock a couple of bonuses in Mass Effect 3 - one is the Chakram Launcher, which is kind of a super-powered charge attack assault rifle, and the other is a unique armor set you get from the beginning of the game. Both of these could be considered somewhat of a cheat. :)
There's a bunch of stuff that is pre-order or only came with the Collector's Edition:
- AT-12 Raider - Origin pre-order bonus
- M-55 Argus - Pre-order bonus for select retailers
- N7 Warfare Gear - Pre-order bonus for select retailers
- Robotic Dog - Collector's edition
- Squad Outfit pack - Collector's edition
- N7 Weapons pack - Collector's edition
- N7 Hoodie - Collector's edition
These are all single player items. The Collector's edition and pre-order bonuses are currently unavailable outside of pre-ordering the game or buying the collector's edition. No news on whether or not those of us with the "regular edition" will be able to buy them at a later date.
There's a couple of single player items that you can get for free by playing the Kingdoms of Amalur demo:
- Chakram Launcher
- Reckoner Knight Armor
There's a Battlefield 3 Pack (a set of multiplayer items) that you can only get by having Battlefield 3 activated to the same account as Mass Effect 3.
There's also the "From Dust" DLC (a single player mission + a new squadmate) which came with the deluxe/collectors editions but is available to anyone (from day 1) for around $10.
In addition to these items, there's a number of Razer ME3-branded items that come with special codes/unlocks for multiplayer.
On top of these, there's a whole set of Mass Effect 3 toys that you can buy, and each one comes with a similar code for multiplayer to the Razer items.
One tally of all the DLC for Mass Effect 3 listed the grand total at $870! However, the codes that come with the Razer gear and the toys are more along the lines of the "booster packs" you can buy in the multiplayer in-game shop, so I wouldn't consider them anywhere approaching essential.
Best Answer
As a general rule of thumb (applies in most cases):
PC DLC codes should be region free.
Console DLC codes are almost never region free.