What's one thing you're really good at that he appreciates a lot?
Just use those skills to your best and that's your ultimate present.
Everything after that is just great add-ons.
...does he like any books? Computer programs? Favorite brand of clothing? Animes? Movies? Styles of bags? TV shows? Etc etc etc...
...the best anniversary gift combo that I use is:
AT LEAST ONE thing made by me.
AT LEAST ONE thing purchased by me.
and AT LEAST ONE odd gift not expected.