It varies tremendously depending on the person. I used to wear watches for functional reasons when I was a kid, but no longer wear watches. With smart phones and spending much of waking hours near a computer or programmable remote, I know longer need a special device to tell the time, and I have more powerful functional features in my phone than I ever previously had in a watch. However, wearing watches for stylistic reasons is a different story. I’m not into style and wouldn’t wear a watch for style, but I know a minority of younger males who do wear watches for this reason… often the types that are into wearing business style attire. Surveys have found a similar pattern.
I’d suggest something that is meaningful and personal to him, focusing on his unique interests and/or your unique common history, rather than a generic popular gift for typical 18 y/0 males.