Karadoc's Apoc Mod - great mod that rebalances and improves many aspects of the game. Pure xcom apoc won't be so much interresting after playing it.
My goals in making this mod were to make Apocalypse more balanced (particularly to reduce the power of toxin guns and disruptor shields), and also the make the game more challenging. I've tried to balance the game so that I will only win if I play at my best (without reloads, etc). I'm not sure how challenging other people will find it.
last verson 0.9 - 5 march 2009 download link: http://www.strategycore.co.uk/files/index.php?dlid=720