Propofol
"Have had propofol twice now (once for flexible sigmoidoscopy and once for a colonoscopy).  It worked wonderfully for me - woke up feeling like I had a long refreshing nap.  I tend to be super sensitive to drugs and usually suffer side effects from them so I am amazed at how good I felt after the propofol.  No lasting side effects at all.  Sorry to hear it was unpleasant for some!"