You might want to try:
Rogue 5/Psychic Warrior 5/Soul Knife 10.
That's a pretty cool PC concept and you'll never be without a weapon.
Also, you could go the TWF route:
Ranger 1/Fighter 4/Rogue 15
The common tactic is to specialize in short swords to maximize your TWF sneak attack damage.
Another good choice is:
Rogue 5/Wizard 5/Arcane Trickster 10
This build gives you most of the benefits of being a high-level wizard. Plus your sneak attacks continue to go up and you get cool abilities like impromptu sneak attack.