hard call. i'm looking for one such build too, and i don't think there is one. at least not one without some shortcommings.
i've seen a fighter/paladin do pretty alone.. about equal levels of paladin and fighter, so this will work for all race choice.
i've got a rogue/fighter/shadow dancer who's kickass with the right items for the situation. she requires some inventory space to store multiple items like swordsman belt, rod of the ghost, to be used at the right time, but being able to use practically any item means she can take on dragons alone, with a scroll of negative energy.. requires SOU
a pure monk might be good, but unless u simply want the WIS to AC, as in druid/monk or something, i see little point of multiclassing a monk.
clerics always make good solo characters, with the right spells. u're healer, tank and spellcaster all in one
i'm currently planning for a sorceror/paladin, and wondering about the dragon disciple class... research, research..
of course the style of play between some characters here might put some ppl of from opting for them.. anyone with other suggestions??