On the other hand, if he goes ranger then he doesn't need to meet prerequisites so pumping strength makes more sense.

Anyways, I'm going to go out on a limb and suggest a 1-20 build:

Halfling Fighter/Rogue/Shadowdancer
STR - 14
DEX - 16
CON - 12
WIS - 8
INT - 14
CHA - 12

1 - Rogue - ambidexterity
2 - Fighter - two weapon fighting
3 - Fighter - weapon proficiency (exotic), weapon focus (kukri)
4 - Fighter - increase dexterity
5 - Rogue
6 - Fighter - weapon specialization (kukri), weapon finesse
7 - Fighter
8 - Rogue - increase dexterity
9 - Fighter - dodge, mobility
10 - Shadow Dancer
11 - Fighter
12 - Shadowdancer - improved two weapon fighting - increase dexterity
13 - Fighter - improved critical (kukri)
14 - Fighter
15 - Rogue - iron will
16 - Fighter - knockdown - increase dexterity
17 - Shadowdancer
18 - Fighter - toughness
19 - Shadowdancer
20 - Fighter - improved knockdown - increase dexterity

I'd absolutely toss in knockdown pretty much right away.
Say 3rd level and skip kukri, going with weapon focus rapier the second hand weapon could be whatever happens by. Dagger, Handaxe, Whip. Or rather not take weapon focus at this point, but rather finesse, that giving the same bonus.

Basically, leaving knockdown to 16th level, you couldn't use it once in the OC.

Weapon focus is taken there as a prerequisite for weapon specialization, which is an important source of damage for this character. If you want to grab knockdown earlier, I'd say drop exotic weapon proficiency and go with short swords instead.

The big advantage of taking weapon focus early is that the RNG actually pays attention to your feat choice and weights the odds of your "chosen" weapon higher, so it increases your chance of getting a kukri in your treasure. Otherwise yes, it is mechanically no different from weapon finesse at this stage.

That's actually a very good point.

This one will get an EXP penalty starting with lv4.
Elves have wizard as favoured class if I remember correctly.

This is very good.
When I will play NWN1 I wanted to make a fighter/rogue myself.
But it will be completely different, more strength based.
Motto:
If it shows your back to you, backstab it.
If it sees you (which is very likely with heavy armor and a giant scythe), steal his weapon (improved disarm), knock it down and stomp on it when its lying before you.

This leads to a question importend for both of us:
Does (improved) knockdown allow sneak attacks when the victim lies before you?

Yeah, knock them down and then sneak attack when they're helpless. Works like charm.

My favorite combat rogue so far was about 2/3 Barbarian and 1/3 Rogue.
Was thinking about Conan as a guideline when making him.
Decent enough lockpicking and such, pretty bad sneaker.

But high tumble, with good attack. Sneak attacks with Greataxe are lots of fun!
Barbarian also gets more skill points than fighter, which helps.

I thought more of Darth Vader.
Fighter4, blackguard7, rest rogue (not in that order, of course)

I hope the best heavy equipment is black and I get a purple glowing scythe.

Argh, I knew I must have overlooked something >_<

Yeah, this either needs to be a halfling (in which case strength is going to suffer) or it needs to be rejigged to use more rogue levels and fewer fighter levels. I'm going to edit him as a halfling.

Actually, I just realized that I only did a 28 point build up there; I have enough left-over points to take a Halfling's strength to 14, so yeah this works without further modification as a halfling.

Here's an Elf Rogue/FTR build I put together way back when I was posting builds on the Epic Character Builders Guild forums:

FTR 20/Rogue 19/HS 1

Playable from level 1 to 40, PvM.

Elf, any non-evil

STR: 16 (18)
DEX: 17 (32)
CON: 12
INT: 14
WIS: 8
CHA: 8

1 )Rogue1: Two Weapon Fighting
2 )FTR1: Weapon Focus:Handaxe
3 )Rogue2: Ambidexterity
4 )FTR2: Weapon Finesse/ DEX (18)
5 )FTR3
6 )Rogue3: Knockdown
7 )Rogue4
8 )FTR4: Weapon Specialization/ DEX (19)
9 )FTR5: Improved Knockdown
10)Rogue5
11)FTR6: Improved Two Weapon Fighting
12)Rogue6: Toughness/ DEX (20)
13)Rogue7
14)FTR7
15)FTR8: Iron Will/ Blind Fight
16)Rogue8: DEX (21)
17)Rogue9
18)FTR9: Alertness
19)FTR10: Improved Critical
20)Rogue10: Improved Evasion/ DEX (22)

21)Rogue11: GRT DEX I (23)
22)HS1: GRT DEX II (24)
23)FTR11
24)FTR12: GRT DEX II (25)/ Epic Weapon Focus/ DEX (26)
25)Rogue12
26)FTR13
27)Rogue13: Defensive Roll/ Epic Dodge
28)FTR14: Epic Weapon Specialization/ STR (17)*
29)Rogue14
30)Rogue15: GRT STR I (18)*
31)FTR15
32)Rogue16: ESF:Discipline/ DEX (27)
33)FTR16: GRT DEX IV (28)/ Armor Skin
34)Rogue17
35)FTR17
36)FTR18: GRT DEX V (29)/ Epic Prowess/ DEX (30)
37)Rogue18
38)FTR19
39)Rogue19: GRT DEX VI (31)/ ESF:Spellcraft
40)FTR20: Epic Toughness I**/ DEX (32)

It's easy enough to switch out the Harper Scout and sub in Shadow Dancer, and since it ends up with +17 BAB at level 20 as posted, you can take the SD level any time you want and still maintain a full attack routine. As well, if you don't want to min/max, you can lower the starting DEX to 16 and move those two extra points to CHA.

This build keeps the FTR and Rogue levels balanced so there's no XP penalty. I played the build as posted through a handful of modules and it worked great. A really fun build to play.

(If anyone is wondering why the Harper Scout levels, I was in a period where I was enjoying using that prestige class, and it allows you to choose Great Dexterity as the HS bonus feat if you take it in epic levels - and there were tons of FTR/Rogue/SD builds posted at the time already, so I went for something a little different).

The combo comes naturally; Fighter takes the edge of the shadowdancer feat prerequisites and lets you get your full attack progression, while Rogue lets you easily meet the shadowdancer skill prerequisites and grants you sneak attacks that synergize nicely with the prestige class.

I don't blame anyone for running a F/R/SD build; it's fun, it's straightforward, it works smoothly at all levels, and you've got plenty of leeway for customization. My first F/R/SD was a halfling who used a Katana and balanced strength and dexterity. Not optimal, but it got me through HotU just fine.

Yeah, I've played a ton of Rogue/FTR/SD builds and like I said, there were plenty posted on the Guild at the time and I really couldn't add much new to the list, so I went for HS instead on the build. But as I noted, it's easily adaptable to SD instead of HS (and would likely be much easier to play since you get to use the HiPS spam and have all those sneak dice for delicious damage dealing).

A problem is that NWN1 use DD3.0, which is not so good (NWN2 uses DD3.5).
You can find some better classes using the 3.5 mod for NWN1, but it is not very easy to install it:
http://www.gog.com/forum/neverwinter_nights_series/dandd3_5_for_nwn1

With 3.0, I was compelled to play multiclass Ranger/Rogue/Fighter to have the Ranger I want, with 3.5 the Ranger class does not need multiclassing.