The Anti-MechanicG 20

This is another accumulitive achievement over the course of the single-player campaign. You will easily kill well over 50 enemy vehicles as they include tanks, jeeps, even the golf carts on 'Par for the Course', as well as turrets and etc....

There is speculation that if you kill a vehicle with more than 1 enemy, for example a moving tank with an active gunner on top, it counts as 2, but there are plenty of enemies to kill in vehicles that it really doesn't matter. I netted this cheevo about half-way through the game.