I played a Paladin/Rogue of Kelemvor once
created after encountering one too many Lawful Stupid paladin players.
Statistically, the race was hengeyokai, the GM was letting me play it as a wererat.
I played her in a PbPost on Mythweavers for a year and a half and successfulyl had the other players thinking she was a human rogue with a high UMD and lots of stuff. I did this without ever lying or otherwise breaking the code.
Also, a key feat for paladin/rogue exists for 3.5 in Complete Adventurer...I believe anyway, my books are in another country...think it was called "Divine Inquisitor" upshot, gave you a benefit of some sort forget what exactly, and allowed Paladin and Rogue levels to stack for smite and sneak attack.
And somewhere, there was a feat that let sneak attack work vs undead.
EDIT: Oh, I remember the benefit now, when you used a smite at the same time as a sneak attack, they combined for extra effect somehow