He didn't want you to have an irrational fear of germs, and use that to get sympathy and special treatment at work. After you catch his cold, your fear of germs will be rational and well-founded. Then you can add a heaping helping of paranoia to list of mental illnesses. With OCD and paranoia, delusions of grandeur add a nice kick to the Crazy Stew.

That's when you take some of your feces & smear it all over his desk chair & keyboard !!!!!

Tell your boss!!!.. Or.. Get back at by sabotaging his lunch

Wow OP, fyl. But seriously, as a cynic, this amused the hell out of me. No matter how gross it is, ocd or not, its somehow made hilarious because you're a germaphobe.

That's a sticky situation

Shit on their car

Sneeze a bubble snot and stick it to HIS mouse then get a video of his reaction XD

That´s gross, no matter if u have OCD or not! :S

That's fckn gross. You should take revenge, whether it's by telling your boss or actually getting done one of the previous proposals.

Wow. Just...wow. I hope you went to your boss, OP. I'd love to see the coworker's file after an incident like that. "Bob spreads germs like an inconsiderate jerk." Try to not stand too close to him. He's probably also stopped showering and will rub up on you to spread the wealth.