Does the person that you want to get even with drink red wine? If so, have I got one for you! Get yourself some Neutral Red, a water soluble, crystalline red dye. Mix some into the persons wine and wait for them to take a leak. (Nuetral Red comes out as red as it goes in, and people have a tendancy to get really nervous when they start peeing what they think is blood!
Does the person that you want to get even with drink red wine?