Picking a birthday gift that pleasantly surprises your girlfriend involves paying attention to her likes and dislikes. Think about her hobbies, passions, and interests. It could be a thoughtful piece of artwork, a romantic picnic in a scenic location, or tickets to a show or event she's been wanting to attend. A surprise element, such as a scavenger hunt leading to the gift, can add an extra layer of excitement and anticipation. Keep in mind that the key is to make her feel special and appreciated on her birthday.