I have Realistic Fatigue/Encumbrance and I have played FCOM. Currently my game is challenging and fun for once. Is there any other mods that make the game more hardcoe?

Yes. http://www.gamesas.com/index.php?/topic/1120709-relz-rom-revised-oblivion-mod/. bliviongate:

http://www.gamesas.com/index.php?showtopic=1010109

Check the Immersion, roleplay and "any mods?" lists.

(The any mods list has about 3-4 topics like this)

Rambling:
I wonder why no one has created a "sims" type realism mod. You know, stuff like:

*You haven't talked to any friendly people in over 2 days, you are very depressed*
*You have been wearing Daedric armor for 5 days and even slept in it several times. You are extremely uncomfortable*
*You pissed yourself in the middle of town. You are very dirty, and embarrassed.*
*You haven't done anything you consider fun in over 12 hours, you are soooooo bored!*
etc.

I mean, sure you could say that it takes away from roleplaying, because: "what if I'm a hermit, or a wild druid, why would I be getting lonely or depressed without people?!" but even that could be handled by having a customizable ini and maybe like a list of optional traits at the start of the game like:

"Druid: Social, and fun is increased by being around animals." (Maybe have some downsides to each like: "gets dirty quicker", or "no social/fun increases from activities involving people.")
Hermit: No social requirements. (downside maybe... "Sweats profusely around people", or some other downside related to people/society)
Warrior/archer/mage/thief/etc: These would effect what you character considers "fun"/// Mage=reading/training, Warrior= killing monsters. Archer = long distance shots? etc.

Personally, I don't use any "realism mods", but a system like I described I'd probably use, even if only for the novelty of it.

A little bit hardcoe: NoEncumberedSwimming

http://www.tesnexus.com/downloads/file.php?id=3331



This one sounds good, sounds like another game...

http://www.gamesas.com/index.php?/topic/1053088-deltes-thread-of-immersion-mods/

...or better, don't go to the above thread (Delte's thread of Immersion mods #25), but rather to http://www.gamesas.com/?showtopic=983734, since he for the two latest threads wanted to build a simpler mod list without many of the immersion mods.