When I look for prizes and presents for students, I look for things that are gender-neutral, non-licensed, fun and interesting. (Don't look here for Disney princess toys.)
If they're vaguely educational, that's a bonus. If they're just silly and fun that's fine too. Here are some favorites.
I once had an extremely agitated student who was completely soothed by a liquid motion toy like this. His mother seemed so mystified that I gave him the toy on the spot even though it was an "expensive" prize. Having raised an extremely challenging child myself, I wanted to help in any way I could and a Liquid Motion toy was the least I could do. I like to play with them, and the multicolored ones are the most satisfying and beguiling. Some of them are quite elaborate.
These magnets are interesting and great fidget toys. They repel each and attract each other and the "buzzing magnets" actually do make strange buzzing sound when you rub them together.
My students like anything fidgety. I particularly like quiet fidget toys, because as a parent I always appreciate toys that are fun to play with and quiet.
The classic Chinese Finger Traps are not durable, but they are a lot of fun for $.19! When you put your fingers in them, they "trap" your fingers when you try to pull them out. A sure-fire hit with little ones who've never seen them before.
These little solar dancing toys amuse my students because they don't use batteries. Sometimes I keep one in my front window near the piano.
Kids have always loved Silly Putty and if you buy a bunch at once it's relatively inexpensive.
I advise against buying anything other than the Silly Putty brand because the other ones often don't work as well.
These little handheld games have some kind of odd attraction in these days of high-tech video games. There's something calming about playing with little rings in water.
I keep some of these magnetic colors stones around because they're very strong magnets and they're fun to play with. Not particularly quiet, because the magnets are so strong, but kids like them.
This little timer is fun because the sand floats UP instead of down.
Anything about Ladybugs is always a good idea in my studio.
I use a coil keychain just like this one every day. If I'm carrying things, I can just slip my keys over my wrist and I don't accidentally drop them.
This Flower Pen is about as girly as things get in my studio. I love flowers and keep fresh flowers around, so I couldn't resist this Hibiscus pen.
The Tangle toys are excellent fidget toys. They are soothing and silent. An excellent backseat toy for the car.
Magic Loops have been around since I was a little girl. My piano teacher had them as prizes in her studio. Some things never go out of style.
I'm including a few items not really suitable for students gifts, (unless you have a bigger budget than I do!) that your own children or grandchildren might enjoy. The River Crossing Game is one of a number of brilliantly designed games from ThinkFun. Each of these games has adjustable levels, so as one's skill increases, so can the challenge. My kids also enjoyed Hoppers. Both of these games are self-contained though they have lots of small parts. They're great throw in a bag for waiting rooms or traffic jams.