My very favorite idea is the old-school bowls +1 game if there remain 2 undefeated teams.  Even if that means there are 3 undefeateds after the bowls and it becomes a beauty contest.
If no undefeated teams remain, it's a beauty contest anyway.  Don't like it?  Don't lose.
In such a system, Miami and Washington would have played in '91.  Michigan and Nebraska in '97.  Auburn vs USC in '04.