I don't have a son to buy for but I work with teen boys and some of the things I reckon the lads I work with would like, or need, include:
Stationary items - even the basics like pens etc - big pack of biros for example! Even if they don't want it, many of them are forever losing their pens and desperately need it.
Fidget toys! Many of the lads I work with absolutely love these! Popular ones are often the classics like stress balls, fidget cubes, fidget spinners. There are so many available now!
Spray deodorants - they love spraying the stuff around and coating themselves with it! Lynx seems enduringly popular.
Books. If they already like reading, get them more of what they like. If they don't, encourage them if you can! Loads of the lads I work with really like manga, currently. Popular series with the lads I know include Demon Slayer, Dragon Ball something or other, Tokyo Ghoul
Sweets, especially unusual stuff. I took some Japanese sweets in recently and these were devoured, especially some weird jelly tube things that looked repulsive to me.
Hair styling stuff, combs, even seen a few of the lads with pocket mirrors when they aren't allowed to use their phones to check their hair...
Don't rule out arty and crafty stuff - more lads than we think love drawing for example, so some decent pens or pencils. Even a little craft kit might go down well with some - I ran a craft activity recently and was surprised how many lads got stuck in and loved it.
Merchandise of their hobbies and interests (be that football team, bands, TV or game characters). My DD last Xmas got her then boyfriend a Five Nights at Freddie's plushy, and he was genuinely thrilled!
Vouchers! Again based on DD's ex, anything for food places like Greggs or Maccies - or fave shops, Primark for example, or in this one's case, Waterstones!