The current trend to use plastic clamshell packaging that is welded shut (to minimize shoplifting) is a curse for consumers. The plastic is thick and tough, creating ideal conditions for wounding yourself when trying to open it, particularly if you attempt it with a knife.
We found that "crash" scissors, modified by removing the foot on the lower blade, will safely deal with the toughest of these packages. You just cut off a corner to get access to a single layer of plastic and then cut along one side.
Of course, the serrated stainless-steel blades are still great for cutting wire, thin sheet metal, leather, or fabric.
7" long overall.