Wired has a neat gallery that looks into the robotics labs at SPAWAR in San Diego. There's a wide array of ground-based humanoids, vehicles, and other machines, which all appear to be armed. On one of the bots:
This prototype robotic weapon platform is designed to be buried underground for camouflaged deployment. When called to action, the robotic gun pops up and starts shooting. If you're the unlucky soul on the business end of this gun, it's likely curtains for you -- this robot is an extremely accurate shooter. A high-tech night-vision scope (bottom right) permits dead-on targeting even during moonless nights.