Wires are exceptionally useful tool for a shinobi. Though by itself it isn't that useful, when used in a combination with other weapons, it can be dangerous. The most well known use for it is by Uchiha Sasuke against his fight with Orochimaru. He uses it with the combination of shuriken and kunai knives. With the wire he can connect to the opponent with his Fire jutsu accurately.
Shikamaru uses the wires with the combination of exploding tags to make the fighting field booby trapped. This allows him to controls the path of his opponents which is extremely needed for his signature move, the Shadow Bind jutsu. He does this twice, first in The Legend of the Stone of Gelel and his fight against Hidan.