The most common foods that are fermented include dairy products, grains, and fresh vegetables such as cabbage, cucumbers, and fruits. Meat and seafood can be fermented as well.
There is an endless list of foods that can be fermented since there are many ways to adapt to the process of fermentation such as using fermentation as a part of the food production process.
You may be surprised to know that fermentation is used as a part of the manufacturing process to produce chocolate, coffee beans, and white pepper! All of these ingredients are actually the seeds of fruits with thick and pulpy outer shells. To remove the tough exterior and get to the seeds (aka bean), the fruits are harvested and wet-fermented. Once the seed is removed it is dried and processed.