A pendant in the shape of Thor's hammer Mjollnir. Usually made from bronze or silver and worn around the neck on a leather thong. Archeological findings suggest that pendants like these were used as amulets by the Old Norse (including vikings) and are very popular today in Sweden, Denmark and Norway.
Many people wear them to show pride in their history but also to mark that they are non-christians (Wearing small silver or gold christian crosses is also very common in these countries). It does not necessarily mean that anyone wearing a hammer pendant believes in asatru, though. | 
