I'll share some of my bathroom related ones (so that I have more to share than just the previous CBT tutorial) :D
The floor of the tub/shower falling through the ceiling due to water damage. That's an old one I had for years, probably from ages 13-23 or so. Gone now, thankfully.
Someone looking through the door crack or standing on the other side of the door lurking. Almost entirely gone now, but once in a blue moon this will occur to me for a second. I laugh at this one because I often leave the door open regardless of what I'm doing, so when this thought pops up it's just so silly.
Slipping and falling getting out of the shower, but that's a legitimate risk :P I could buy a new tub mat.
Towels being too dirty, but I've dealt with this by stocking plenty of towels and being willing to (mostly) use towels that my family has used before me. I still rarely dry my hands on towels in anyone else's home. I sense this may not even be that OCD, but I can't objectively comment on it at length for obvious reasons.
And the old classic... snakes coming up from the toilet. Still gets me at night when I'm groggy, but also easy to laugh it :)
My sons getting into pill bottles. Nothing will truly help with this other than a locked medicine cabinet, so I have most of them stashed away. The funniest part of this is that there aren't even any prescriptions in my home, so I'm obsessing about ibuprofen, Tums, and vitamins. Not something I think about unless it comes up usually, since I have a system, but whenever anyone brings prescription bottles into my house and leaves them on tables/counters I have to move them somewhere safer. One of my remaining compulsions, but I don't mind it.
I had the stabbing in the shower one for a long time, too. Can't remember the last time I worried about that, years and years, but it was one of the hardest. I really did not like living alone or being at home alone. You might want to get a roommate..
A new one is breathing in the "spray" from the toilet flushing without the lid, so I've started closing the lid before flushing. If there's no lid (like in public) then I time it so I'm turning my back to exit the stall immediately after flushing. New O's are weird. I don't mind this one, because the only thing I think will happen if I breath in the toilet mist is that maybe I'll catch a cold from the bacteria.
My lipstick having germs on it. But if one color is striking me as "germy" then I use another color.
Wow, there are more of these than I thought there'd be and this is just the bathroom. I could go room by room :)