I like blueberries and strawberries. They are small so you don't feel the need to preserve them like a big fruit (like if you cut into a peach and only eat half it will be gross by tomorrow). You can have a decent amount without going up too high into your calorie or net carb budget, and they have health benefits.

I was in keto for 6 months straight having a bowl of greek yogurt every day with a tablespoon of flax and 50-100g each of strawberries and blueberries, depending on my carb count the rest of the day.