I am about to start a new character on 360 and will impose rules on my game, here are some of the restrictions I will be implementing.

Perma-death, this I feel may be too much for many but I like the challenge, the difficulty will be hard as very hard, which I usually play just won't work with ammo restrictions.

No fast travel, the use of fast travel as a safety feature doesn't really sit well with me neither is using it to quickly take a horde of crap to a good merchant to get rich quick.

No vats for combat unless undetected and are able to get first shot in. No using In danger mode

No healing during combat, must be safe to heal

Carry capacity set to 100

Repair at merchants or workbenches only

Barter amount with traders set to zero, can only purchase items using pre war money

Broken limbs can only be healed by a doctor, same with addictions and rad removal

Two ranged weapons max with one of melee or unarmed , one two handed and one single handed or only one big gun. Only 3 grenades and mines allowed to be carried. No more than 5 full reloads for each weapon.

I'd say no companions but if you have them then you have to pay them per day for their assistance.

Turn off hud completely

Can only carry one stimpack at a time

These are a few I'm considering using thus far, any suggestions for improving or new ideas would be welcome.

Some more I'm considering.....

Endurance and intelligence set to lower than 5

No taking the op perks... grim reaper, silent running, cyborg etc

No obtaining the skill books and bobble heads

No power armour, light armour only.

Nice ideas, I also use these:

(1.). Carry miscellaneous items which you would use - hammer, wrench, duct tape,tweezers, scissors. If you wish, you can repair anywhere if carrying tools.
(2.). Carry items for cooking - metal pot, pan, fork, knife. How else will you cook and eat your pork & beans?
(3.). At level up, add points to skills used on previous level (ie if you shoot 2 enemies with a pistol, pass 3 speech checks, repair 1 weapon, sell goods to 3 traders, pick 4 locks, assign your available skill points to the relevant skills at level up).
(4.). Cannot heal, drink, eat or repair while in combat (up to you if this is Danger or Caution status).
(5.). If you have the patience for it, walk everywhere unless appropriate to run. More for realism than challenge.

Here's a thread you might be interested in: http://www.gamesas.com/topic/1176044-fallout-3-hardcoe/ I think the suggestions made by mpls Big Daddy are particularly interesting.

The extra items carried for repair/eating is a good idea, I'll definitely be using it cheers. Also only adding to skills I have used the previous level, is a good idea ill just have to keep a dedicated fo3 notepad just to keep track between sessions. It's also a pity that experience gained amounts cannot be tweaked... surely you should get less on very hard and the most on very easy instead of the other way round as the levelling goes by far too quickly