An Oyster Shucker is someone who opens oysters.
Usually use a flat-bladed screwdriver to tackle the hinge.
In the past, by the way, oysters were looked down on as a cheap food for the Common People. Don't know what happened to turn them into the desirable and pretty pricey things they are today.
Here's how pro's shuck an oyster...
http://www.bbcgoodfood.com/videos/1022/shucking-oysters