[mad=dog]

My best three char game was with a Kensai->Thief PC, Aerie and Edwin. My main char was Lawful Evil interpretted as loyal, but selfish. I had a mix of companions on the third slot to compensate for shortcomings during the dual phase before Edwin joined to complete the trio.
A Kensai->Thief has a shattering backstab - nearly as good as an Assasin->Fighter - but better thief stats. This includes a maxed out ever vital Dispel Illusion score to compensate for Edwins shortcomings in this field and provide near-instant disposal of misleads, mirror imgs and similar. I wouldn't even bother with a thief unless Dispel Illusion is high. An Assasin->Figther is also very very good, but with slightly less in AC and worse thief skills (though you can work on Dispel Illusion enough to make it to max when you dual).

I have also toyed with the idea of a Swashie->Mage, but found the Swashbuckler class to be broken as you did not recieve any benefits from the ability to specialize.