Fallout 3 is an awesome vanilla game, I know. I love exploring the the wasteland, going through every abandoned structure whether it's a bus, house, factory.... or anywhere! -- But it's not challenging enough.

I tried playing on Very Hard, but that does nothing but waste more precious ammo.

So, is there any mods which add fear and a need to survive, like if I see a deathclaw, I don't just think "Oh it's just a deathclaw... stand and shoot and he will die", I want to be like "AHHH a deathclaw, *save game* get up on a spot were he can't get me and shoot my best weapon".

I will be checking out the Fallout 3 Hard Core mod so don't say that.

There are quite a few. Check out this: http://fallout3.nexusmods.com/. Go to the Files button and than left click on catagories. There is a whole section on gameplay. I use FWE-Fallout Wanderers's Edition. It can be configured for difficulty.

I can do that, I asked here because I'm too lazy!

I've been using the nexus for FNV for over a year now, I'm no noob!....until I got banned.....

What you want in your game is fear and uncertainty ..

I use FWE mods, impervious power armor , MMM mods

FWE is a great mod with massive changes and several options. Increase damage/Reduced loot and you can set the game which ever way u like ..
MMM spawns a whole lot of creatures(which can be custom set)
Impervious power armor is for later game when i see the Enclave and say (F**K IT, am outta here)

Another thing u can do is set rules for better game play..

carrying only 1 armor and only 2 weapons and a melee weapon... not more than that and you save only at towns...

With the above mods and these rules, for get death claws... even raiders will make you sweat
and you get to experience the unforgiving wasteland

Thanks! I'll check these out soon.

Wow, FWE is and awesome looking mod... I cannot wait to try it!

If you really want hardcoe, try arwens realism tweaks http://fallout3.nexusmods.com/downloads/file.php?id=7565

Be warned, you WILL struggle just to survive, let alone against any creatures.