Boeing C-17 and Ilyusion Il-76
Keeping in mind that bush planes come in all sizes and shapes and, that by definition bush planes are operated in remote locations out of small strips, the C-17 and Il-76 are the largest bush planes in world. Admittedly, they are a far stretch from what most people would consider bush planes, but these aircraft have both seen their fair share of rugged and remote areas. Bottom line, if a person (or more likely, organization) needs to haul a ton of cargo or passengers to an incredibly remote location, the C-17 and Il-76 are the only practical airplanes available. Other, even larger planes arguably fit this category (such as the Lockheed C-5 Galaxy and Antonov An-225 Myria), but neither plane has operated in as rugged and remote locations as the Boeing and Ilyusion.
These are both very large airplanes (and neither are offered in kit form!). The Boeing is a newer design and may cease being produced in the next few years (depending on whether Boeing obtains new orders). The Ilyusion dates from the late 60s and is still in production in Uzbekistan. These planes are literally capable of hauling battle tanks and are included in this website only for general interest. The organizations operating these aircraft are well aware of their need for such and aircraft and even though bush-planes.com is a world renowned and mighty website, it is doubtful anyone will decide he or she needs a C-17 or Il-76 because they looked like the right plane for their job based on this website.