A Rammer Trukk.

The battering ram and the kannon on the bulkhead behind the driver were taken from the gorkamorka wrekker trukk

The driver and gunner had their heads removed and new heads added from the ork boyz plastic sprue.

The glyph on the front comes from the Fantasy Orc shield sprue.

Click here to see the bitz I bought from GW mail order to make this model.