USATODAY.com has details on Spec Ops "survival mode" in Call of Duty: Modern Warfare 3, the upcoming military shooter sequel (thanks Computer and Video Games). Here's a bit on that:

As we dispatched ever-increasing waves of enemies, I discarded my pistol for a shotgun. Rubin passed me some in-game currency and I bought and installed a turret to keep the evildoers at bay, while I watched for attack dogs.

After a few waves, the attack dogs became suicide bomber dogs that exploded a few seconds after you shot them. The next wave brought the kamikaze soldiers who exploded similarly.