make a chocalate cake out of your shit, your girlfriend's shit, his girlfriend's shit, and if you can somehow find away to get some of his shit, that as well.
if he smokes, put one of the cigarettes in your butt, and tell him about it. it's great. cause if he smokes them, he gets ass. if he doesn't, he's wasting his monies.
This thread is epic. Set up a live web cam on your roommate’s shower. Send a link to the cam to his friends, parents, coworkers and girlfriend from his email address.
This need a bit of effort from your part and only works if he isn't a douchebag and if he might have had sex outside his relationship. Either way, you go to the nearest drug store or any kind of store that sells pre-paid sim cards. Which will get you a new phone number. Now from the new phone number send him a text saying you have chlamydia and that he probably has it aswell. And is obligated to warn all his sexual partners that he might have contaged. Tell him a date from about half a year ago or when you know he might have been shitfaced and might not remember with whom of if he has had sex.. Watch him panic and desperately send texts to all kinds of girls and enjoy!!