PsyWar with the Alternate Class Feature that lets them make their own weapon?
I mean, to expand on what Sinfire said, they've got class skills that indicate a stealth focus, but no stealth-related class abilities and not enough skill points. They've got a solid hit die, but they're shackled to meleeing without heavy armor, which necessitates Dex and Weapon Finesse and increases MAD, which mixes poorly with their Medium BAB. Plus they're stuck with a Short Sword, barring extra feat expenditure, so they don't get a useful Power Attack. They don't have to pay for a weapon with gold, but they pay for it with class features and they get improvements way more slowly than the game anticipates; my Soulknife fix makes them stronger by taking away the free enhancement bonuses and making them pay for it themselves, at the normal rate. One of their major class features, Psychic Strike, requires a move action, so they lose mobility and only get one attack/round if they want to use it more than once per combat. Bladewind is just Whirlwind Attack, which isn't good to begin with. Knife To the Soul kicks a fair bit of ass, though. But really, that's a lot of work for one nice class feature in a giant pile of suck.
EDIT: Combined with the Shadow template, you might be able to pull something salvageable out of it, but that's because that template is pretty awesome for LA +2 and more or less supplies the entire Stealth side that the Soulknife needs. I did this once, but this was when my party (and most importantly, DM) was low on optimization-fu and there were still occasions when I felt useless (damn you, Reverse Gravity!). I mean, most of us thought the Tome of Battle was broken back then. So take that suggestion with a grain of salt.
