During a holiday weekend camping trip, I did about 2.
During a holiday weekend camping trip, I did about 2.5 - 3 grams of shrooms one night (and smoked heroic amounts of pot). About 12-15 of us were sitting around a campfire when my trip went off the rails. I started to feel sick and wanted to puke, but was paranoid that if I did, it would ruin the whole night for everyone else. I couldn't think of a way to throw up without anyone else knowing, so I started quietly asking people sitting near me if it was OK for me to puke, and if it would ruin their evening.
They all assured me it would be fine, so I walked over to a big, gnarled tree to puke behind it. The grass around the tree started growing and waving around me, and it seemed somehow threatening, like it was trying to "get" me. I puked at the base of the tree, trying to do so as quietly as possible, because I was afraid of waking up the "Keebler Elves", who I was convinced lived in this big twisted tree.
My next fear was that I was puking too hard, and my vomit would seep into the earth and contaminate the underground Rice Krispie supply. (I think at this point I was confusing the Keebler Elves with "Snap", "Krackle", and "Pop" of Rice Krispies fame).
Afterwards (I thought I'd never stop puking at one point), I sat inside a dark room in our cottage, and felt very physically uncomfortable and anxious. Patterns on the curtains, furniture, and carpet all swam around me. I constantly needed someone to be in the room with me, and panicked at the prospect of being left alone, even for a minute.
I settled down a bit after a while, and had a good time the rest of the night, but I couldn't understand anything that anyone was saying, and the things I was saying only med sense when I said them, but immediately became a mystery to me (and everyone else).
Here's the weirdest part: When I finally went to bed, I lay in the dark for a while, and suddenly I noticed something sitting on the bed across the room from me. It was a life-size cowboy, made of what I can only describe as solid smoke, all grey. He got up, walked across the room, and morphed into Jesus Christ! Then the son of God reached down and tucked me into bed. This was even more odd because I am an agnostic.
It was a bad trip, but I was still glad I had it. Drugs never really freak me out generally, but this was the closest I ever came to losing it. After that, I've been able to handle even the most intense trips easily. Besides, how many times in your life does the savior of mankind tuck you in?