is a remote explosive fetured in every conflict game to date. It is commonly used to accomplish objectives and should not be used freely as a weapon.
Assuming you have spares, C4 can be a useful weapon. It has the abililty to always destroy tanks and APCs. If you lack AT weaponry, throw down some smoke and get close enough to lay a C4 down by the tank. Retreat and detonate and the tank will be destroyed.