Oh Lord
NEVER use glasses/cups in the room unless they come factory wrapped... maybe not even then.
And let's not even mention the coffee maker. I know individuals who regularly do rather foul things to those.
Remember: If you can imagine somebody doing it, somebody has done it.
*Has someone p!ssed in the coffeemaker reservoir? Oh yeah
*Has someone wiped their a$$ on the pillowcase? The same one that you'll lay your head on tonight? Yep
*Has someone (done some completely unmentionable thing) to (something in the room that if you knew about it you'd puke)? You can bet on it