That would be the Unimog, hard as it may be to get your hands on one.
Mercedes makes a lot of sport-utes – some of them (like the G-Class for example) more capable off-road than others (like, say, the GLA). But as well suited as it is to venturing off the beaten path, the G-Class, believe it or not, is not even the most capable off-roader that Mercedes makes.
No, that would be the Unimog, a line of multi-purpose utility trucks that Daimler has been producing, in various iterations, since 1948. That's longer even than the G-Class, which was originally introduced in 1979 and was just replaced by an all-new version last year.
Shorthand for Universal Motor Gerät (or universal motor machine), the Unimog is a highly versatile piece of machinery with a cab-over design and typically fitted with a pickup bed at the back (though often outfitted with other equipment on a chassis-cab basis). It can go just about anywhere you'd imagine sending a four-wheeled vehicle, carrying ten metric tonnes or more of cargo and personnel along with it. And though dimensions vary by application and configuration, it's safe to say that it's huge. No wonder it's used in such a wide array of applications, from military and railroad to agriculture and snow-clearing.
So why don't we hear more about the Unimog? Well, for one thing, it's a truck, not a passenger vehicle. For another, it's not regularly available in America. Daimler offered it here through Freightliner dealers over a decade ago, but only sold 184 of them over the course of five years before pulling the plug. So outside of a certain former governator's garage, you're not likely to see many on the road. That leaves the G-Class, for all intents and purposes, as the most capable Mercedes off-roader you can realistically get your hands on. But as you can see from these photos and video footage, in absolute terms, the Unimog reigns supreme.