I used to give my roommates, Celeste and Sir Trick, who were a couple, a hard time because every week or so I'd need to take a piss while they were busy fucking in the shower. When my boyfriend, Sora, moved in, I had to decide whether to take the high road, and not seek vengeance by long shower-fuck sessions, or take the low road, and see if we could make more noise.
For once in my life, I took the high road.
Apart from a couple of noise battles (when you try to prove how much better your sex is by increasing the volume of moans, shouts, and smack noises), we tended to let our sex remain private.
One afternoon, Sora and I were in the kitchen arguing over something stupid, and we heard the roommates getting it on. We ignored it. And after a half hour or so, Celeste came into the kitchen, with a huge glob of come on the front of her shirt. Sora and I contained most of our laughter, and didn't even say anything when she said "Oh my god, dude!", turned around, and ran into her room to change her shirt.
Later that night, after drinking enough Coronas to be declared official citizens of Mexico, Sora and I stumbled into our room for some loud, sloppy, lights out, almost sex. Because Sora had a nasty habit of falling directly asleep after orgasm, we had a standing/sitting/laying down agreement that I always got to come first. So I did. Once devoid of sperm, I knelt down to reciprocate, and Sora promptly rammed his cock into my nose. After the requisite name calling (I chose douchenozzle for this particular occasion) and ass smackage, I forged ahead with the fellatio.
Once he'd come, we made out for a bit, and then Sora decided to take a shower before he fell asleep. He threw a towel around his waist, and walked down the hallway to the bathroom. He was too tired to hear the water running, so when he opened the door, the apartment was filled with all three of my roommates screaming. Sora screamed because he'd walked in on Celeste and Trick's shower sex, and Celeste and Sir Trick screamed because Sora's face and belly were covered in blood. Apparently, he'd rammed my nose harder than either of us had realized.
The next day we put memo boards up on our bedroom doors, and the bathroom with "Occupied" and "Vacant" signs.