I have many, but this is my favorite.
I wasn't out yet, and I was dating this guy. We were in a band together. We are both silly and strange and morbid, as you will find out. We were going to have a barbecue, so another band member and I went to the market to get some carne asada. Well, the market also sold blood. By the pound. I thought, this is too good. There will be something weird I can do with this. Some strange practical joke. So I bought 1/2 a pound of blood.
We go back to the house, and I find a hiding spot for the blood in the back of the fridge behind the Sunny D or whatever the fuck. Meat and veggies were grilled, we sit down to have dinner. We have been drinking this whole time. I wasn't keeping track. I used to drink like 15 beers in a sitting (I have slowed down a lot since my early 20s).
At some point, I excused myself and went to get the blood. I secretly moved it to a spot in the bathroom, where I made it look like I had a bloody nose. Just a little bit though. I pretended to freak out about it, bf remains calm and helps me by applying pressure, etc.
A while later, I did it again. He was still so calm about it (he ended up becoming a paramedic a couple years later - totally not squeamish about blood) - I figured my joke was ruined if he wasn't going to flip out. So I told him that it was all a farce, and that I had bought him a present. I went and got the blood and there was a gleam in his eye.
He poured it on his head.
I blacked out a little around there. The rest of the night consisted of us having a dirt fight, him going to buy cigarettes covered in blood and dirt, me drinking an entire bottle of shitty wine by myself, walking on the railroad tracks, almost getting arrested.
Needless to say I did not make it to the bathroom in the middle of the night to pee, and that was at the very beginning of our relationship, so it was extremely embarrassing.
TL;DR: Blood, dirt, piss.