Extremely similar to the post above, I use Allegiances rather than alignments. Allegiances are not a houserule but come from d20 Modern. Allegiances include Good, Evil, Law, Chaos, in addition to allegiances to the King, Knighthood Order, Church of Blahblah, Guild of Yadayada, etc. Note that one can have a maximum of three allegiances, but many people don't have any allegiances at all. As such, a paladin must obligatory have allegiance to Law and Good, plus maybe to a Church or a Knighthood order. A person who roasts a baby for dinner automatically has allegiance to evil, even if pretending and believing otherwise.
For me, this allegiance system is far superior to alignments. It is more flexible, includes the traditional alignments if need be, but can also include other considerations.