How I'd do it.
Race: Xeph (Expanded Psionics Handbook)
CL 1 - Rogue (Dodge)
CL 2 - Fighter (Weapon Finesse)
CL 3 - Telepath Psion (Mobility, Psionic Weapon) (XPH)
CL 4 - Monk (Improved Grapple, Improved Unarmed Strike)
CL 5 - Ranger (Track)
CL 6 - Psychic Warrior (Practiced Manifester, Psionic Meditation) (XPH)
CL 7 - Hexblade (Complete Warrior)
CL 8 - Sorcerer
CL 9 - Barbarian (Spring Attack)
CL 10 - Elocator (Sidestep Charge) (XPH)
CL 11 - War Mind (XPH)
CL 12 - Slayer (Inquisitor) (XPH)
CL 13 - Duelist (DMG)
CL 14 - Ninja (Complete Adventurer)
CL 15 - Thrallherd (Combat Reflexes) (XPH)
CL 16 - Shadowdancer (DMG)
CL 17 - Crusader (Tome of Battle: Book of Nine Swords)
CL 18 - Swordsage (Shadow Blade, Discipline Focus - Weapon Focus - Shadow Hand weapons) (ToB:Bo9S)
CL 19 - Warblade (ToB:Bo9S)
CL 20 - Master of Nine (ToB:Bo9S)
= Awesome ninja fun, for me, anyway.
Roles: Sneak/infiltrator (primary), assassin (primary), hit-and-runner (primary), chaser/escapee/runner-over-any-surface (primary), mystical martial artist (primary), information gatherer (primary or secondary), detective/lie-detector (primary or secondary), manipulator (primary or secondary), minion recruiter (secondary), scout (secondary), tank (secondary), trickster/tricky fighter (secondary), thief/lockpick/trap-handler (secondary or tertiary), hunter/tracker (secondary or tertiary), outdoorsman (minor), scholar (minor).
Further notes/details:
[sblock]20th-Level Basic Stats: BAB +9/+4, Base Fortitude +20, Base Reflex +20, Base Will +16, average HP overall (D8 on average), decent unarmored AC, 9 power points + level 2 Int-based bonus points from Psion + level 1 Wis-based bonus points from Psychic Warrior + level 1 Wis-based bonus points from War Mind, fairly speedy, sneaky, has some minions and the capacity for additional minions (Psionic Charm), caster level of 1st in Sorcerer (spells are likely Mage Armor and Shield, to be most effective while unarmored as he'd be after reaching 9th-level), good at hit and run tactics, fairly good damage with such (after factoring in feats, maneuvers, powers, and such),
effective manifester level of 5th in either Psion or Psychic Warrior and 1st in the other (I don't recall if Practiced Manifester applies with only one psionic class or not), psionic powers (probably Psionic Charm, Mindlink, Entangling Ectoplasm, Empathy, Call to Mind, Offensive Precognition, Expansion), various 1st-level class features, Dexterity bonus to attack and damage with a rapier or other Shadow Hand weapon (I forget the other weapons associated with that Discipline), all kinds of uses for Dexterity, minimal need for Strength (just 13 to qualify for Psionic Weapon), good uses for high Wisdom so likely to be great at related skills and compensate for the base Will save only being mostly awesome (though Ninja's unspent ki energy pool gives another +2 Will as well, I think), many decent skills and a few good skills especially for stealth and social matters, decent outdoorsman and survivalist, decent favored enemy bonuses, has a familiar (should be a Raven that speaks one of his languages; this would allow him to use Minklink on it, and thereby use it as an effective long-range scout),
initiator level of 11th each in Crusader/Swordsage/Warblade upon reaching 20th character level (Bo9S counts initiator level from martial adept prestige classes, like Master of Nine, towards all ILs), 13-16 martial maneuvers of 5th-level (or lower at the PC's option), 3 martial stances of 5th-level (or lower at the PC's option), 2 or 3 martial maneuvers of 6th-level (or lower at the PC's option), and some access to all Nine Disciplines (potentially; don't have to take maneuvers/stances from each, but easily could).
Would probably want a Keen +5 Rapier or the like (to help make the attack bonus decent, after adding in Weapon Finesse and Weapon Focus and possibly other things), and a Ring of Evasion (due to mediocre HP and the lack of 2 straight levels in any of the classes they have which would normally provide Evasion at 2nd-level), as well as possibly a Ring of Protection +5, Amulet of Natural Armor +5 or Amulet of Health +6 (likely the most useful items for their neck slot, since they won't need extra good Wisdom, just plain good Wisdom, and HP may be their main weakness as a frontline character; they should otherwise do alright on the frontline, with their good AC, awesome saves, martial maneuvers, damage/stat-boosting feats/class features, and Expansion psionic power).
I forget what all the prerequisites of the Master of Nine prestige class are, but I think I covered most of them or all of them with the feats I put in this build. If not I'd just have to swap out one or more of the early or middle feats (Psionic Weapon, Psionic Meditation, Improved Grapple, and possibly Practiced Manifester are expendable; but they're really useful to this I think, and well, IG is just an automatic Monk feat; I don't think Stunning Fist would be as useful to this build, since its abilities would otherwise be rather focused on a magic weapon like the rapier). I also forget the exact number of maneuvers a 1st-level Crusader, 1st-level Warblade, and 1st-level Master of Nine each get (I've only just started using a Swordsage, and have returned the Book of Nine Swords to the friend I had borrowed it from for the past few days, since I wrote down my PC's maneuvers/stances and their effects).[/sblock]