Very nice mod for XCOM
Long War http://xcom.nexusmods.com/mods/88//?
Major Features:
* Eight soldier classes. The classes are: Sniper, Scout, Assault, Infantry, Gunner, Rocketeer, Medic and Engineer.
* Up to a dozen missions per month. Abductions will take place one at a time.
* Revamped and new perks structured to force difficult choices at each level while creating powerful complementary abilities
* Aliens conduct research and their soldiers and UFOs will grow tougher over time, although X-Com can slow their advance
* Interceptors gain experience and grow more accurate
* SHIVs now have the potential to be a major component of your tactical game
* Strategy game rebalanced; everything takes time to build and research and satellite spam is no longer the dominant path to victory
* Expanded Gray Market and council requests for alien captives
* Many new items, alien pods of up to six x-rays, alien leaders, and much more!