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!