Years and years ago, My big brother got dumped the day before valentines day (girlfriend of 2 years revealed she had been cheating on him with his "best mate" for 6 months..) so he and I went out on a walk to find some roadkill. That day was his lucky day because, Hours later, we found a west highland terrier puppy that was as flat as a pancake, so scraped it off the tarmack, took it home, folded it (that bit was NASTY) and put it inside the valentines day card he had bought for princess back stabber a few days earlier.
Revenge - So sweet.
The downsides? We didn't get to see her reaction