Landmines are the perfect example of existing autonomous technology. Next steps would be, I imagine, drones that fly themselves home if jammed. Still pretty innocuous but a step into automation.
Also imagine a first generation turret. Automated target acquisition based on stereo imaging and stereo microphones. The first models would require an operator to approve the target. But the systems are so much faster than us - soon you'd want to be able to approve a target area, hold down the "OK" button and have it keep firing. We're not talking spray and pray here - this thing could be single round fully automated sniper, catching someone who only sticks their head up for a fraction of a second. How long until you'd designate an area as a no-go hostile zone and leave it on all night to guard the perimeter?