Wartrakk
Wartrakks are one of the most common and used Ork vehicles. Cheap and relatively effective, they are the Ork equivalent of a Rhino but with more firepower than transporting troops. Essentially a Warbuggy mounted upon a sturdy track unit, a Wartrakk sacrifices its speed for the ability to traverse rough terrain such as a ruined city and deliver heavier firepower.
Usually most Ork warbands are accompanied by a ramshackle band of Wartrakks that hurtle around the battlefield shooting at anything they can. Most Wartrakks come with a twin-link Heavy Bolter/Big Shoota which makes it great for both fast assaults and clearing light infantry, as of 7th edition they and the Warbuggies can get a twin-linked Rokkit Launcha for free. Que in endless Lulz as you have a relatively fast anti-tank platform. They are also relatively cheap so you can try and spam those if you can. Of course they are still as lightly armored as the Warbuggies so a simple swift breeze can dismantle the entire thing.
Wartrakk Skorcha
Essentially the Ork's take on the Imperial Hellhound the Wartrakk Skorcha are Ork Skorcha heavy flamethrowers mounted on a Wartrakk chassis. Consisting of a mounted tank of promethium, Wartrakk Skorcha's specialize in incinerating the enemy with great sheets of flame. The crews of these vehicles are usually Burna Boyz for whom man-portable burnas just aren't enough. Usually they have a Gretchin to mend the promethium tank so that it doesn't overheat and blow up in their face.