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Rogue/Swashbuckler, with the Daring Outlaw feat that allows Swashbuckler and Rogue levels to stack when computing Sneak Attack or Grace, might be fun. You can pick whichever you like to specialize in melee vs. skill monkey and still get excellent results.
Yeah, Swashbuckler/Rogue/Swordsage (2-3 SS levels really adds to your swashbuckling capabilities with swift action jumps, hits with both weapons, sense motive-based AC and all that) is the archetypal "Sneaky Warrior".
Warblade makes for a decent option too, particularly with a Diamond Mind focus, and straight Swordsage works too. It is, after all, more about which skills you want; Rogue/SS gets more and has better SA. SA Thug Fighter is also fairly decent for that job.
Really, ToB adds a lot to Swashbuckling; with it one-handing is even somewhat viable (tho most of these builds really want two-weapon fighting).