Make a playlist of songs that remind you of a time you spent with someone, then give them the "tape".
Plan a treasure hunt for kids - or adults! We hide Easter eggs around the office without telling people to see how long it takes them to realise 😂.
... but not for yourself. Plan a day trip, weekend away or (if you are feeling brave) a holiday for someone else.
Everybody should feel pampered. Give someone a day pass for the spa or create your own spa at home and invite them around.
Throw a surprise party for someone - it doesn't have to be their birthday, it could be for a completely silly reason.