The engineer unit characterizes with relatively low health but high speed. He can equip submachine guns as his primary weapon which grant him awesome close distance combat skills.
Engineers can also equip rocket-launchers as their primary weapons - they are effective against both tanks and infantry units on the battlefield. Try playing with a rocket launcher - you will surely have fun to throw your enemies around like bowling pins.
The strategic advancement of this unit is to build stationery heavy machine guns to provide great suppressive fire and metal shields for good cover. Just take out your wrench and all the magic begins!