LEGO stormtrooper variation
These are promotional items. Not from a set. They can be related to a store-opening, a give-away, other special events, etc. Looking through the Bricklink catalog I found one listing with a stormtrooper torso that you might be referring to: http://www.bricklink.com/catalogItem.asp?P=973pskac01

If you can add a picture we can probably identify them more precisely. Hope this helps some...(c;