2K Games just released an update to XCOM: Enemy Unknown that addresses a few issues and adds even more replayability to the already very replayable campaign. In addition to the expected minor bug fixes, improved touch controls, and better use of system memor, they’ve also included a new option called Second Wave that allows players to adjust the following:

Damage Roulette: Weapons have a wider range of damage.
New Economy: Randomized council member funding.
Not Created Equally: Rookies will have random starting stats.
Hidden Potential: As a soldier is promoted, stats increase randomly.
Red Fog: Combat wounds will degrade the soldier’s mission stats.
Absolutely Critical: A flanking shot guarantees a critical hit.
The Greater Good: Psionics can only be learned from interrogating a psionic alien.
Marathon: The game takes considerably longer to complete.
Results Driven: A country offers less funding as its panic level increases.
High Stakes: Random rewards for stopping alien abductions.
Diminishing Returns: Increased cost of satellite construction.
More Than Human: The psionic gift is extremely rare.

Get to it, Commander!

source: 2K Games