Biff
The HVY Biff is a large industrial truck that is featured exclusively in Grand Theft Auto IV. It has dump truck and flat bed versions. The Biff is a prominent vehicle in Derrick McReary's Tunnel of Death mission; you must use one to block the Booth Tunnel. The Biff is a slow vehicle to drive due to it's weight. But can be a bit of fun when ramming cars and squashing the section of the car almost flat and taking very little damage yourself in the process.
Design
It closely resembles a Mack Metro-Liner, however these trucks were only manufactured and sold in Australia and New Zealand, so it may be based on a Mack Granite, however with a shorter bonnet (which makes it look more like a Metro-Liner).