Depending on the class of course, but usually I will go with 16, 16, 12, 12, 10, 8. Especially if the secondary stat for the class is Dex or Int (say for my gnome Feylock). AC and reflex defense are just too important.
If I want an 18 pre-racial (say the race doesn't give a bonus to the prime stat, and / or gives bonuses to the scondary / tertiary stats [like a dwarven fighter], or the class is especially single stat focussed [like an archery ranger]), then I will go with 18, 12, 12, 12, 10, 8.
The third option, which used to be my preference but has since dropped down the list is 16, 14, 14, 13, 10, 8 (or 12, 11, 8 or 12, 10, 9). But often the secondary stat is more important than the third defense, so I don't like this one as much anymore.
For some reason, I think it is the powergamer in me, but I really hate starting with odd stats, as then you have a left over stat point (from leveling up) at level 30, and that just seems like a "waste."