Okay, let me just say it out loud. Houseguests are fine until they overstay their welcome or pull one of those typical houseguest things that they are known for.
And, really it's not just me. I found a thread on Reddit where people got honest about all things their houseguests have done to them.
1. "One of my best buddies from high school called me up and begged for me to come get him from a town. The idea was he would stay with us for a couple of weeks while he looked for work and then get his own place. Six months later I ended up renting him a room for one month and dropping him off with his junk and wishing him well. " - squidazz
2. "My dad's friend pissed in the corner of the guest room, and asked for money from everyone who happened to walk by him." - Seemose
3. "Couple came for a weekend to my small apartment, surprised that they brought 3 dogs and an extra friend. The puppy took a dump on my floor in the night, which nobody got up to clean. Another dog had a crate but managed to get a hold of a carpet outside of the crate, drag it in, and shred it. They also chewed up cardboard and wooden furniture. When they left, all the shredded stuff was just where it fell. - neon_dave
4. "She stole all of my booze, pissed on my couch, tore up the flower bed to the side of my driveway, and destroyed my guest bathroom. This all happened after I'd fallen asleep, she was a guest of a tenant/roommate, and that roommate was told either her friend wasn't allowed over again or she'd have to find a new place to live." - amalgamas
5. "Instead of asking where the toilet paper is, they let their kid wipe his ass with our guest towels." - __Dawn__Amber__
6. "My mom's cousin and her husband went for a short visit to our house. She was five months pregnant then. She and her husband didn't leave until the baby was two months old." - MinutesTaker
7. "Wife's cousin stayed a couple days with us. After he left, I discovered he purchased about $60 worth of porn on directv." - TheGentlemanLoser
8. "My parents came over, and started snooping through my closet while I was making tea. They found some sextoys and proceeded to get mad at me for having them. In my own house. In my own bedroom. They wouldn't have found them if they would've behaved like normal people." - UnusualRedditter
9. "My dad owned a business his whole life and was in the process of hiring new installers. One applicant came in from out of town and my dad offered for him to stay in our home. When the morning came the man went to take a shower. My parents heard the water turn on and it stayed on for a really long time. After an hour and a half of running water, my mom made my dad go check on him. My dad went upstairs, picked the lock on the bathroom door, and found blood and a limp body on the floor next to the running shower. The man had overdosed, lost consciousness, hit his head on the shower side, and died." - A_Hale
10. "The husband of my great aunt came to visit us, mind you he was like 80 something years old, so he goes to the bathroom to do his business, and he comes down, now he smells a little bit, but we all brush it aside then when he sits down and after a while gets back up to leave, you can see shit stains on the sofa. Not only that but my mom then goes upstairs and finds the bathroom full of shit, not full-on shit but a bunch of it was sprayed in the walls, etc. " - Aioli_Tough
11. "My father-in-law threatened to beat my 6-year-old sister because she was running around on our porch." - CoffeeAndPizzaRolls
12. "Husband of a friend came for X-mas since she was out of town. He brought the dog who had diarrhea. Dog humped our dog for hours till our dog was covered in s**t." - Ibenthinkin2much
13. "A high school buddy of mine called to ask if his late-teens daughter and her two friends could stay at our house for a night, as they were travelling. We even gave them our master bedroom, and master bath. They announced that they were staying for six days, actually assuming we'd let them have our room the entire time. We said, no, one night of fun, then down to the basement. They left the next morning when we were out, didn't say thank you, took a bunch of snack food." - Marlowebabe
Yikes, this has got to hurt.