When I first joined Conquer Club it was exclusively because I could play the traditional Risk map. For several years I only played the Classic or other "simple" maps where the strategy was strictly straight forward with no special rules. I started to look at the other maps which I considered stupid as a challenge and realized that by playing them it caused me to think and thinking is good. Alzheimers runs on my Dad's side of the family and as I am now in my 60's the thought is always lingering as to whether my mind will fade away as I have seen in other members of family. Here are a few of the maps that I have played thus far that I would consider to be the most challenging for a first time player and probably should be banned for new members until they become established a bit.
All Your Base Are Belong To Us
Bamboo Jack
Battle For Iraq!
Conquer Rome
Cricket
Das Schloss
Forbidden City
King's Court
Monsters
Poison Rome
Stalingrad
Supermax Prison Riot!
Trench Warfare
Woodboro