I can't get the link to work.
I love old and unique church buildings, but I'm anal about saying church buildings
. Churches are assemblies of people; not buildings.
*Edit: The link ended up working--I've been to the Washington National Cathedral, but before it was finished. I'm surprised my favorite is not on the list--Hagia Sophia in Istanbul, but maybe it's not on the list because technically it's now a mosque.
There is also St. Anne's in Jerusalem, notable not for its visual aesthetic but for its acoustics which are absolutely incredible.