Hardest Zombie Escape map

1) What do you think is the are the top 3 most challenging zombie escape maps today ?
Ridorana cataract t4
Valkvang (csgo)
last man standing


2) What map do you think is pretty old but still quite difficult and challenging - maybe underrated?
fapescape
skyrim
infected sewers

3) 3 maps which are rarely played (can be any difficulty) but should be played more.
Genso of last
Last man standing
Valkvang