Freshman year of college - 19 years old.
I went with a friend to a frat party (we weren't thinking of rushing, but for $5, we got to drink as much as we wanted, so we just pretended to be thinking about it), and he had a much weaker tolerance to alcohol than I did at the time, so he talked me into drinking two beers for every one he had, so that we could "stay on the same level." Very fucking dumb.
I proceeded to get ridiculously drunk. 14 beers, a funnel of straight vodka, rum shots, and some other shit I barely remember. Way, way more than I should've had.
Over the course of the night, my friend and I were talking to these two girls, and they invited us back to their dorm room. When we got there, the girl that I'd been talking to got a call from a friend, and said she had to go. So I told my friend that I was gonna head home and pass out when he took me aside and tried to talk me into a threesome with him and this other girl. I told him I wasn't into that, but to have fun. He then asked me to just come up with them, because he wasn't really interested in her, and just wanted to hang out a bit as a group. I said sure.
At this point, I blacked out. I have no idea what happened between saying "Sure" and waking up in a pitch-black dorm room with my pants around my ankles. I couldn't see anything, but I could hear my friend and that girl hooking up. Now, keep in mind, in that mental state, I wasn't really able to form complete sentences, and could really only repeat things I was hearing. I heard my friend say "put it in your mouth," and then I said, "Shmmyeah, putty inyermowt." Then he told me to shut up, and I did.
But then I started to feel my stomach turning a bit. Now, I'd never vomited from alcohol, so I brushed it off. And no later than that thought leaving my head did I start projectile vomiting. All over the dorm room - the desks, the other bed in the room, and what I later found out were their books and laptops. Not knowing what to do, I did the only thing that came to mind - I pulled up my pants and ran the fuck out of there. Miraculously, I didn't puke on my clothes at all, so I ran home, got under the covers, and woke up to one of the worst hangovers I've ever had.
The story doesn't end there, though. See, they didn't know I threw up at the time. According to my friend, I didn't make any noise when I vomited, so it just sounded like I'd spilled water on the ground/desk, and they continued with what they were doing - specifically, he was going down on her. But when the odor of what had happened reached his nose, he had a really bad reaction - he vomited, also. Only, since he was going down on her, he actually vomited a bit inside her.
Needless to say, they turned the lights on and saw the whole crazy scene. To this girl's credit, she played it super cool. She was rubbing my friend's back saying, "It's okay. We can clean it up in the morning..."
"The morning?" my friend replied.
She realized then that my friend was planning to bail, and she took his keys, putting them on her nightstand. So my friend went along with it for five minutes, then, when she wasn't looking, grabbed the keys and ran home, leaving her with this insane mess.
I never saw that girl again, but I'm told she wasn't pleased. And, I mean, duh. We were such assholes about not sticking around to clean that up. We deserved a whole lot worse than someone thinking we were dicks.
Anywho, that's probably the worst night that comes to mind for me.