If you're wondering what to buy me for Christmas, don't even consider gift certificates. It's like giving currency as a gift but the currency of some limited geographic use like the Slovenian tolar. I'm sure Slovenia is a lovely place and they may have wonderful things I may consider buying for myself but why do you want to limit me to shopping only in Slovenia?
Advertised lately are gift certificates for a collection of various stores or restaurants under a larger corporate umbrella or gift certificates that can be redeemed at any store inside a particular mall. Again, why limit me?
If you insist on giving a gift certificate then consider giving the most useful gift certificate ever invented: Cash. It's accepted in every establishment at the mall, in every restaurant, by any street vendor and if it's US cash it's probably accepted also in Slovenia.