Think about the various interests that you both have and plan something that can mark this significant milestone.
Plan a weekend getaway to a place you've always talked about visiting together.
Some gift stores and websites have created their own lists of suggestions but nothing as widely recognized as the wedding anniversary symbol list first created by Emily Post in 1922.
However if you have a good thing going, it is important to let your partner in the relationship know that you appreciate them.
You can surprise your significant other with this, or you can simply plan the evening together.