Ogre is a hex-based wargame designed by Steve Jackson and was published as the first Metagaming Concepts Microgame in 1977, It was later reprinted in 1982 by Steve Jackson Games. A expansion with new units (Shockwave) and a sequel (G.E.V.) where released for it, as well as a 1:285 scale miniatures game and a GURPS setting book.
The general premise should be familiar with anybody who has read the Bolo novels and short stories (by Keith Laumer and a lot of other authors): One player controls a gigantic cybertank armed with huge cannons and a number of missiles. The other player controls a assorted conventional force of tanks, G.E.V. hovertanks, artillery, and infantry, and must protect their command post by destroying the weapons and treads of the Ogre. The majority of weapons being some flavor of nuclear, with the odd railcannon tossed in, resulting in an extremely high-casualty experience.
G.E.V. focuses on more traditional ground combat between the North American Combine and the Paneuropean Federation. It included new rules for terrain, overrun combat and cover. Rather than the blasted and cratered landscape of Ogre (most weapons are nuclear, remember?), the included map has a more traditional semi-urban design with towns, forests and water.
The expansion Shockwave included new units such as super-heavy tanks and anti-missile laser towers.