CK House rules for me...
- cannnot excommunicate dukes / kings
- can only claim province titles, no duke / king titles
- can only usurp duke / king titles
- cannot force-vassalise people outside my realm (unless they are a rebel, or I have a claim on their title, or I have king / duke title over their land, or if they are immediate neighbour)
- must force them to recognise my titles if I win (no more prestige exploit)
- marry within culture or neighbouring culture
- cannot force-vassalise heathens, only annex
- cannot recognise titles of force-vassalised rebels (no more -BB exploit)
- roleplay by trait (eg if I am Selfish, choose option that gives or is most likely to give Selfish trait)
- expand into neighbouring provinces only (or reasonably accessable by sea)
- dukes may only have one duke title (no "super-duke" WC exploit)
- may only revoke title of counts and dukes who own titles that they reasonably shouldn't (e.g. Duke of Leinster owning province of Saracusa, I can revoke his ownership of Saracusa)
- titles will be handed out to same-culture courtiers / vassals
- it is acceptable to F12-die courtiers that I don't want (they are "exiled" by my command)
- cannot start wars or assassinate if ruler has Honest, Just, Merciful, Forgiving traits (however if he has more "evil" traits then this can be exempted)
- males can only have court titles (except for spymaster, who can be female

)
- play by Iron-man rules (cannot revert to a previous save if things go wrong!)