This will win his or her heart and it costs next to nothing!
Get yourself a pink set of Post-its and a big fat sharpie. Write about 20 quick love notes on the Post-its, and then, in the middle of the night, on the bathroom mirror, position the Post-its in the shape of a big heart.
Then, when she or he gets up in the morning - their reflection will be in the middle of heart. And she or he is stunned. And later tonight... well you know.