a million bajillion AC
Um, infinite AC is pretty easy to accomplish.
Dwarven druid x / deepwarden 2
use the spell enhance wildshape (or get the feat that does the same)
and use call lightning or any other method of getting electricity damage. (a pin enchanted with shocking attribute for 1damage +1 bonus +electricity)
Every electrical attack against you, you gain 1d4 con. Every 2 con, your AC goes up by 1. You could use your full array of attacks with the pin, doing 6 damage a round to your self, but gaining 3d4con, for an average of 7.5con/round, or 3ac and 60hp/per round. in one hour of attacking yourself, you should be at +450con, for +225AC and 4500hp, more if you have haste. Attack yourself 1 time per hour to keep the decay at bay.