The enthusiast problem: they already own the good stuff
A golf lover is the hardest golfer to buy for, and the reason is simple - they have already bought themselves everything obvious. The clubs are sorted, the bag is stocked, and there is a decent chance they own two of anything that lasts. Buying more equipment risks landing on something they already have, which is the one outcome worse than a boring gift.
There are two ways around this. The first is to buy a premium version of a thing they use up anyway. The second is to step outside the bag entirely and buy something that belongs to the identity rather than the game. Both work; guessing at a piece of gear they might not own does not.
Match the ball, don't guess it
A dedicated golfer has a ball they play, and it is rarely a random choice. The single highest-confidence gift you can give is a dozen of that exact ball - it is the thing they quietly ration because a lost tour ball in a pond stings. To find out which one, look in the bottom of their bag or the pocket where the box lives; whatever brand is in there is the answer, and matching it needs no golf knowledge from you at all.
Go sideways into the lifestyle
The most reliable enthusiast gifts sit next to golf rather than on the course. A golf-ball whiskey glass, a piece of gear with their team or country on it, or a classic golf book are all things a well-equipped golfer is delighted to receive precisely because they would never buy them for themselves. This is the same logic that makes the has-everything page work.
The one big gift that's safe - with a check
If you want a single impressive gift, a laser rangefinder is the classic, because plenty of keen amateurs still don't own one. But rangefinders are the most-duplicated golf gift there is, so do the two-minute check first: look on the outside of their bag for a small rectangular pouch clipped to the strap. If it's there, cross the whole category off and buy the balls.
What to skip
Novelty gear ages badly with a real enthusiast - the joke headcover gets one laugh and then lives in a drawer. So do off-brand golf balls, which a golf lover recognizes instantly and reads as a budget decision rather than a thought. And clubs, putters and shoes are all fitted or sized to the person, which makes them close to impossible to buy blind. When in doubt, spend the money on a better version of something consumable rather than a gamble on something permanent.