Snake Eater's great-grandpa
Basically, the world is in an energy crisis, until a biologist named Dr. Kio Marv invents the oil replicating microbe called OILIX. OILIX seems to be the solution the the world energy crisis, that is until Dr.Marv is kidnapped by a rouge African military nation called Zanzibar Land. Your of course, Solid Snake, a lone FoxHound agent sent in to rescue Dr.Marv and recover OILIX. In the usual Metal Gear formula you job is to do this without being seen. And for how old this game is (1990) they give you a good amount of options to do this with. You can hide behind objects, keep your distance or if worst comes to worst hide under a table or two to get through the day.
This keeps you from just killing everyone in sight.(Don't forget the trusty cardboard box. Couple this with creative objectives such as attracting carrier pigeons using your C-Rations to hatching an egg that may or may not contain a Snake. You never feel like your doing the same thing you just did.
The bosses are just as creative as the objectives, at one point you have to find a way to kill a man who is so fast that you can't catch him before the gas filling the room kills you instead. Or kill the man with a machine gun hiding in the foliage. The only bad things I can say about this game is that a lot of the time calling people on the radio for advice, while sometimes funny, is almost never helpful, this in turn makes you unsure of what your next objective actually is. All in all, for such an old game to still be fun, it means a fantastic effort.