Propofol
"Went in for a colonoscopy yesterday. I was pretty anxious but they reassured me that I would fall asleep within 20 seconds and wake up and ask when I'm having the procedure. They had me turn over on my side and told me they were administering the propofol, and there may be a burning sensation. I felt nothing, and I was probably out in less than 3 seconds. Woke up feeling perfectly fine, no soreness and no wooziness like I had just been knocked out."