Galvanized Wire 14 gauge
14-Gauge x 100 ft. Galvanized Steel Wire
http://www.homedepot.com/p/OOK-14-Gauge-x-100-ft-Galvanized-Steel-Wire-50142/100200924 $6.29 for 100 feet.
Note that even though this is called "galvanized" it is really just zinc plated to its life is limited outside.