Hilton Niagara Falls, Ontario. I'm only HHonors Gold. Last month for my wife's birthday I put a comment on the website booking to mention it. Granted we stay there frequently, but she got: Birthday card signed by entire front desk staff and a small jar of candied strawberries and blackberries, then a bit later another delivery to our room of a large bottle of Voss carbonated mineral water from Norway and a small box containing four tubes of chocolate liquers, each with a different flavor: Port, Sherry, Champagne, etc., and another card signed by the front desk manager and assistant manager. Upgraded room.
At breakfast next morning a complimentary piece of cheesecake with strawberry toppings.

Other times at other hotels: Mentioned our anniversary and got a large chocolate mousse big enough for both of us to enjoy, and in the hotel's restaurant at dinner a large square plate with four different types of deserts.

At another hotel for either my or my wife's birthday we've received a small box of chocolate truffles (and since she likes them so much, I usually get one).

Point is, don't be embarrassed or shy about mentioning your occasion when booking or at checkin, be it a birthday, anniversary or other special occasion. Worse that can happen is there will be no recognition, but perhaps some small surprise will make for a more enjoyable stay.

bj-21.