Everybody has a list, either mental or physical, of a number of small tools they would like to acquire, if and when they get around to it.
I learned several years ago to make such a list available to my relatives at Christmas time, so that they could find things I actually wanted/needed, and would not buy me a Craftsman dog-bone wrench, or an electric tape measure, or a lighted ratchet, or some other dumb tool that sounded cool to them, but would end up in a box in the back of a cabinet in my shop. My wife, daughter, in-laws, etc. can find things from $5 to $100 on my list.
Maybe mention this to your dad, letting him know that you would much rather get him something that he needs, or will use, than something that he may or may not even want.