Halcion by itself is normally not an amnestic, but it is often combined with multiple other agents and those combinations have rarely been studied.
Alcohol is the classic, but usually requires long term high dosage when used on its own and will have side effects most likely when the person wakes up. It also can potentiate the effects of other things such that smaller dosages can have more significant effects, but also a higher risk of complications, like apnea, permanent brain damage etc. Anyone remember Karen Ann Quinlan?
Rohypnol (sp?) as said above can have true black outs, where people recognize that there is a gap in their memory and so know that something happened.
Ketamine is more of a dissociative they will probably remember strange distorted images.
Propofol (aka milk of amnesia, but I've only ever seen it give IV) is a classic with little side effects.
Versed (a relative of valium) has been known to cause retrograde amnesia. I often had patients who could not remember what I told them in the pre-op holding area before they were given the versed by the anaesthesia personell prior to going back to the OR.
