Nothing compared to some of the wacky shit in this thread, but... I was at a work party for someone who had worked their for a long time and was moving, and I felt the need to show up a co-worker of mine. I brought a 1/5th of Smirnoff and dared him to chug some with me. He only agreed if I mixed it with something. We were both drunk, and so I pretended to mix it with some lemonade. These were 12oz cups, mind you, full to the brim of Vodka. I said go, and we both started drinking our cups. He sprayed his all over the counter, and started swearing "this shit is straight" as I finished my cup. Being the big man, I then grabbed his cup and took it all down and slammed his cup on the counter. 24oz of Vodka in under a minute.
Fifteen minutes later I blacked out. I puked all over my bosses couch, my co-workers girlfriend, broke two jars and a lamp from collapsing in his living room, and remembered none of it. I woke up the next morning with dried puke all over my shirt. Oops.
The best part? I still work there today