Modern naval mines probably qualify as 'robotic' in some sense.
I'm not sure what a heat-seeking missile is; a human decided to fire it, but after that it's autonomous. How is that different in principle from a robot which is activated by a human and is autonomous afterwards?
And a bullet is out of human control once you've fired it. Where do you draw the line?
This rather serious report should be of interest to LW. It argues that autonomous robotic weapons which can kill a human without an explicit command from a human operator ("Human-Out-Of-The-Loop" weapons) should be banned, at an international level.
(http://www.hrw.org/reports/2012/11/19/losing-humanity-0)