It depends on what he likes. Generally, boys like something innovative and practical. I will briefly mention a few things, and you can choose from them:
Since you can be called a best friend, you must know him very well. The first thing to do is to prepare something he has always wanted but has not bought as a gift; it is also good to choose some creative small accessories as gifts. For example, you can engrave your own name on a necklace or mobile phone chain. You can make a doll based on your own photos. If he is a music lover, you can give him a commemorative edition disc; if he likes sports, you can give him a commemorative edition sportswear or sports shoes.
Gifts vary from person to person, and the most important thing is to be thoughtful.