Flowers say "I went to a store." A Birthday Slop tribute says "I've been clocking your behavior for years and I have receipts." Drop the things only you know — his irrational opinions, his signature moves, the phrases he says way too often — and let the AI build him a full birthday website that roasts him affectionately from every angle. Spirit animal portrait, a quiz only you'd ace, awards he definitely earned. He'll love it. Funny tone is the move, obviously.
More memorable than flowers. More personal than anything else on this list.