Sounds silly, but my husband loves to do rc cars with his older kids but hardly ever buys them for himself. The ones we have are busted up, but he won't throw them away because he just loves it. I saw one while I was looking at gifts for the little kids and I'm going to get one for him. It's not a traditional "adult" gift (def an inner kid thing), but he has everything else, and he'll use it to play with the kids, which is the true meaning of Christmas, I think. 😉
Getting my husband a gift card for a massage always goes over well.
i’d go for something personal. can’t go wrong and if he has everything, remind him of the most valuable thing he has.. you! maybe engraving a flask/ whisky glass? maybe a wallet of sweater with a photo of your stitched into it? or skip that and do some seductive photos of yourself? sometimes guys are as simple as women and they just want an evening planned for them. take him out for a special date night?
Is there a skill he wants to learn? Give him a course for that skill. I bought my husband a metallurgy class at a blacksmithing workshop for Christmas. He loves smithing as a hobby, but having him learn more about smithing metals would benefit him.