My first was an Imperial US Officers Ulster 916, given to me on my twelfth birthday, November of 1961.
(No, it's not pink. It's a very definite red. See the third pic for correct color using flash.)
I still have that knife. For what it's worth, the only reason I still have that knife is that it was in my pocket with me at school on the day that our house burned to the ground, destroying everything that we weren't wearing, carrying, or driving.
For my oldest daughter, I bought a genuine SAK (four blades, don't remember the actual model) for her when she was five. In the course of moving around, she lost it. She had difficulty opening and closing it at five, and I probably should have held off until she was seven. By then her fine motor skills and hand-eye coordination had much improved. Her ability to keep track of her stuff had also improved. So, in this case, five was too young, seven would have been better.
I could probably have held off until she was ten, really. My enthusiasm for knives and early acquaintance and ownership would not be denied, however. Live-n-learn.
For my son and youngest daughter, I gave them each a SAK when they were about 10-ish. Christmas stocking stuffers.
I believe both of them have lost theirs. In his case I think it was a result of moving, in hers it was a case of showing it off to "friends" who stole it. They were both pretty much responsible with them, other than his having trouble keeping track of his stuff, and her having trouble picking her friends.
I have since updated them both with newer pocket knives and fixed blades.
He has since lost (or had "borrowed") a very nice Kershaw classic 3120 pattern, and chipped the blade on another. She has since had yet another handful of her favorite knives stolen by one of her friend's brothers. She's still having trouble picking her friends. She is, however, learning that you don't show off your favorite things to people whose trust quotient has not yet been determined.
Once they had been out on their own a bit, they were able to better appreciate their knives, but it's not likely they'll ever become real cutlery fans.
My oldest daughter, however, keeps and cherishes a few of the knives I've given her over the years.
A couple of years ago, my daughter and her family had been living with us while they got their stateside legs under them (they'd been abroad), and I had my granddaughters in the house with us. When she and her husband finally landed a dream gig in Oregon, I helped them pack for the trip, and then I sat down with the (little) girls and their mom. I showed them their knives, and explained what a "trustee" is. Once they understood that their mom would be keeping the gift until they were ready for them, I handed them to their mom with the solemn charge that she should see to it they were properly groomed in the handling of cutlery and given their own when they could demonstrate they could use them safely.
Interesting bonding moment. The older girl is nine now. Gettin' near time, I reckon.
Time it right, assure yourself that the child in question has already had the opportunity -- under guidance -- to handle sharps and use them properly.
It's part of gettin' ready to be a grownup.
Kids get that.
Oh, BTW, about keepin' track of "stuff" . . .
It is very possible -- and I have demonstrated it more than once now -- to give a child too much stuff.
Not in a figurative "spoiled rotten" sense. I mean physically too much stuff.
When you're giving a kid presents, watch and see whether the kid can keep his stuff organized without needing someone to follow him around and tell him to do it. If things never get put up, if things are always going missing, if his stuff is always a mess, then he has too much of it. He simply isn't ready to organize that much random motion.
You can't enforce order into an environment where there are too many particles to track.
Do the kid a favor, don't overload him with things. Try to pick the important things, the meaningful things.
A kid with "too few" things isn't deprived. He has an environment he can control. If you pay attention, you can find the "too much" threshold without exceeding his ability to organize it.
These are just some thoughts from a guy who has had "too little," has had "too much," and who has put his kids through those things, too.