Right now, I've got a Deep Halfling Rogue 3/Swashbuckler 3. He fights with two daggers, get's a +12 to attack with them, and deals 1d3+5 damage (+2d6 sneak attacks) when he hits. He's an absolute terror when he sneak attacks.
He can very easily multiclass into either the Invisible Blade or Master Thrower PrC (or both!), depending on whether he'd rather fight melee or ranged.
He wears no armor, and carries only the smallest weapons, so he's exceedingly inconspicuous. With a Handy Haversack, a Ring of Sustenance, and a few AC enhancers, he's a virtually independent scout for the party.