Subway plans a $2, six-inch sub sandwich promotion for the month of December. The deal is good only on meatball and cold-cut subs. In a still-struggling economy, the chain that set the industry standard with $5 foot-long subs is throwing down yet another gauntlet that's certain to raise industry eyebrows and lure deal-seeking customers. Several other major fast food chains also dabbled this year with $2 meals – including Taco Bell, Chipotle and some regional KFCs.