Overrated - coke, alcohol, heroin (if only b/c it's just another strong opiate), shrooms (if only because I never got anything near what my friends did out of them...and poisoning yourself is really not that fun), and MDMA (I am not a very social person and a drug that pushes me to socially interact with others is just not very desirable)
Underrated - pregabalin & gabapentin (I find them great both medically and recreationally, I have fibromyalgia, and one of their main side effects for me is plain 'ol euphoria), meth (I put it on the same level as many psychadelics), MDA (SOOOOO much different than MDMA - feels natural, and like the whole damned earth was communicating with me), and weed (can smoke it every day, but when I don't it's like an earth-shattering psychadelic panic attack - even crap-ass schwag)