The Engineer is a class that specializes in vehicles and close range combat. His weapon of choice is the SMG, and as such those and the shotguns is the only primary weapons you can buy . He can also repair friendly vehicles with his Repair Tool.
Besides repairing vehicles, he also excels at destroying them. The Anti-Vehicle RPG is a powerful tool against enemy vehicles, which can take down even the most heavily armored vehicle in just a few shots, you start out with a basic amount of three rockets, if you train "Increase RPG ammo" to the max you will have five rockets, this is a very good move to do and as such should be done in the first two levels.
It is affected by Tracers and as such if a vehicle is traced, (If traced you can see a white box around it no matter where you are), the rocket will home in on the vehicle after being fired. The driver of the target vehicle can still use countermeasures, which causes the rocket to go in the complete opposite direction of the vehicle. The rocket will also always home in on the closest traced vehicle.
You can also set "AV mines" (Anti-Vehicle mines) on roads to destroy any enemy vehicle that rides over it. At the current time they can also be used as C4 to stick enemy vehicles and when they move the mine will blow up.
You also get an "Repair Tool" that is used to repair friendly vehicles if damaged, you get points for doing this and as such is a very smart move to make whenever possible, just make sure you are standing behind the vehicle away from the enemy spawn.