Well, that all depends on the coworker's interests and personality. A good gift could be something practical, like a nice pen or notebook. If you know they enjoy a particular hobby, you could get them a related item, like a new set of golf clubs or a gift card to their favorite store. You could also consider something more personal, like a thoughtful card or a nice framed photo. Ultimately, the key is to show that you care and took the time to think about what they would like.