The vannon is a truck with machine guns on the side.
What happens when you combine a car, a cannon, and the craziest Tank drivers around into one Vehicle? You get a Vannon. Vannons are THE cheekiest defensive vehicle that any pigment army can field once they reach level 28. They do what Tanks don't do, which is charge enemies WHILE shooting and turn pigments to a mess on the front grill. Their cannons are also not cannons, but rather AUTOMATIC MACHINE GUNS with a similar projectile as a sniper rifle. Instant.
This defense is helpful, and although they can't run over troops, they can drive themselves into a large group of enemy soldiers and gun them down before they have a chance to fire.