I'm personally a big fan of the unarmed swordsage. Even without armor proficiency, you can grab leather armor, then masterwork studded leather, then a mithril chain shirt and be completely fine for AC, and all the maneuvers to choose from, and fun things you can do, from going invisible, to teleporting around, to shooting fire from your fists, to throwing big hulking men on their asses, it's just really fun and can be so easily built in different ways just by choosing different maneuvers.