When the Mars Company first release new Pretzel M&M's they were using a penetration pricing strategy to entice consumers to try their new product. I was reading the Sunday paper this summer at my parents house, they are old fashion and still get a physical copy of the paper each day, and there was a coupon for a free package of Pretzel M&M's. In this case, you did not even need to buy anything to get a free package of their candy.
This is a great way to encourage people to try the new product. However, it could also lead to cannibalization because most people who decided to try the new M&M's would not also buy an old variety at the same time.