A Gunwagon is an Ork vehicle commonly used as a transport. A basic Gunwagon consists of a powerful engine and a mounted Big Shoota on a chassis. A Gunwagon only has a seat for the driver, but hand holds are provided to transport Orks over short distances. Much like other Ork vehicles, the gunwagon is a highly modifiable platform, and can be armed with a Zzap Gun, a Kannon, or a quad of Flak guns while still retaining its transport capabilities, although the most common chassis used on a Gunwagon is the Rhino chassis.
In addition, the Gunwagon can be up-armoured to protect the driver and gunner, and also mounts an extra Big Shoota and spike armor for extra stabbiness if needs comes to shove.
If the Battlewagon is the Ork's Land Raider and the Trukk as the Greenskin's Rhino than it is safe to say that the role of the Gunwagon is akin to a Space Marine Razorback in both function and usage. Like the Razorback, the Gunwagon acts as an IFV (Infantry Fighting Vehicle) meant to help both carry a modest amount of boyz while hammering suppressive fire towards enemy entrenchments. Although the Gunwagon has an advantage over the Razorback in that it could swap its Big Shoota with the aforementioned weapons to deal with heavy armored infantry, tanks and flyers.
As of 8th edition, the Gunwagon is now a sub-variant of the Battlewagon. It has a built in periscope that lets it fire twice if it moved at least half of its movement characteristic or if it didn't move at all. However, it sacrifices being open topped and has a lesser transport capacity to make up for its extra dakka.
It is overall a really great vehicle and one of the few Ork vehicles superior to that of the Space Marine contemporaries.