Best gifts for developers?

As a developer, we have received such gift on mostly occasions, so t-shirts, customized mugs are very common gifts. We can think about some other customized gifts like Photo-frames, books, cell-phones etc.
A hand watch can be a good gift also. You can also gift chocolates and flowers along with these gifts.

Are we talking conference swag, employee birthday/holiday gifts, or personal gifts? Because each one's a completely different situation, and can depend heavily on whom you're gifting: for example, the run-of-the-mill stuff you mentioned is always going to be a miss for me. I've got plenty of mugs, I don't wear even women's cut printed t-shirts, the only hoodies I'd want to add to my collection at this point are the fancy gothy type, and I don't sticker my laptop, which at this point is about the only way to recognize it easily in a room full of macbooks. But even aiming a little higher, anything that's relevant to my development activity is probably something I'd prefer to pick out for myself. I like good wine, good food, good books, games -- it doesn't have to be about code. In fact it's nice to get away from it a bit sometimes; most everybody's got an aunt who mentioned she'd watched the Kentucky Derby once upon a time and promptly became The Horse Person, foreverafter doomed to be gifted only horse-related tchotchkes. Or another relative in a similar position. It kind of sucks.

Employers also have to step carefully with gifts since your usual branded stuff can easily come off more as disposing of extra swag. The place I work for now has given out laptop bags a couple times over the years (it's definitely a step up from a t-shirt), and does gift cards and baskets for birthdays and holidays.

Books! Does not have to be a technical book, but as long as it matches their professional or personal interests. Shameless marketing :-) dev.to/rommik/10-books-that-every-...

Another nice gift is a subscription to a tutorial, course or a workshop.

Developers like to learn new things and the above mediums are great just for that!

swag socks!

I got from my last customer some powerbanks (beside a mug and cup and so on) . That was a nice gift for me :)

Dev stickers!