There is a mitzvah in the Torah to affix a mezuzah to the doorpost of the house. Our sages say that one who is careful about this mitzvah merits a nice home, and that one should also beautify the case in which the mezuzah is held. The sefer Daas Kedoshim (289, 101) says that the reason one does not use cases of silver and gold is for fear they will be stolen. It can be inferred from this that in places where there is no such fear (such as in the house) it is worthy to affix a mezuzah in a silver or gold case, thus fulfilling "Zeh Keli ve’anvehu."  

These are a few impressive cases from silver and gold.