As I stated in the third incarnation of this thread, I'm not into the brute fighter type characters. I prefer the ones that are more fun to play. So here's my (fun) Monk/SD/Assassin build.
Race: Halfling (+2 Dex, -2 Str) Alignment: Lawful Evil (Lawful for monk, evil for assassin)
Starting attributes: STR 6 DEX 20 CON 12 INT 16 WIS 8 CHA 8 Invest all attribute points into dexterity.
Skill point distribution: Primary - Hide, Move Silently and Tumble. Secondary - Thief skills (Disarm traps, pick pocket, open locks, etc.) You'll start off with 28 skill points at level 1, so don't worry about running out of skills to choose.
When reading this, keep in mind that this build is supposed to be fun to play throughout the game, not just at level 40. That's why I take feats such as weapon focus early at low levels.
Finishing Attributes: STR 6 DEX 32 CON 12 INT 16 WIS 8 CHA 8
Naked stats: AC: 30 HP: 300 (without re-rolling) AB: +40/+37/+34/+34/+31/+28 (I surmise that this is the result of a bug, one which I didn't exploit intentionally) Fort: 21 Refl: 37 Will: 19
You can get an AC of round about 60 to 70 with the correct items, and also a decent AB if you use dex-centric items.
This character is able to function as a trap disarmer, lock opener and pick pocketer; but also rocks in parties where you have a decent tank to absorb damage. With the massive +20d6 death attack, I managed to get sneak attacks in excess of 100. You should be able to take anything on one-on-one, as long as it doesn't have true seeing.
My favourite combo is: Hide Improved Knockdown Improved Disarm Called Shot (Arm for fighters, leg for anything that might run away.)
You also get increased speed (130%), so you should be able to outrun everything but a pure monk.
Another thing to note is that you won't be able to take ANYTHING on fairly. Your damage is something like 1 to 8 -2, which is pitiful. If you want to improve your damage, go elf instead of halfling, and invest all your excess attribute points into strength. Then get an etra level in monk for ki strike +1 and an increase in the damage that your fists do.