A friend of mine made a character build something like Rog 4/ Swash 4/ Duelist 10 (I forget exactly but these are the classes levels might be a little different) . He doesn't wear armor of any kind and has the highest AC in the party. Our DM checked the math on the build and it is accurate. His AC is in the high 40's and now goes over 50+ when he starts to fight defensively or goes totally defensive.
In fact, our DM is so flustered by this build we have been banned from ever making the same build again in his games.
If anyone wants to build a guy that is virtually impossible to hit check out those three classes. Make this build a TWF and you got someone who could slice and dice quite nicely!
On the down side, he doesn't inflict a lot of damage (he is not actually a TWF), but when he uses the Goad feat, none of the bad guys can hit him and the rest of the party just picks them off one buy one.