Here's a wonderful gift suggestion: a lottery ticket with the winning numbers on it. This works very well if your exwife plays the lottery and you know where she keeps the ticket. (hopefully, she plays different numbers everytime so that she will need to look at the ticket to see if she won) .
So if the lottery drawing is on a friday night, play the winning numbers from that drawing on a ticket purchased early saturday morning. Find and replace the ticket she has with the one you bought. Hopefully, some time later, she will check her ticket with the winning numbers and viola: she believes she is a millionaire. Of course that belief at some point will be shattered by the hard ugly truth and it will be the equivalent of you robbing her of millions of dollars.