Okay, feeling the need to post here just to stop you doing something stupid.
Please do NOT try any of the ones above, especially the salt and pepper one (could kill you outright).
There are plenty of "legitimate" (read: crackers but popular) diets that will at least not do you any harm:
Atkins:
Link. Essentially you change most of your diet into protein, eating lots of meat and cutting out carbs. (Caveat here as Atkins WILL cause you massive harm in the long run but you are looking short term)
Chicken Soup Diet:
Link. Sensible breakfast followed by as much chicken soup as you can eat.
Apples only diet: exactly what it says. You can eat as much apple (fresh only) as you want. Do NOT do it for more than 4-5 days though...
Cabbage Soup Diet:
Link Kinda self explanatory.
Please do not do anything like the "X many litres of water a day" crap as they will fuck you up royally.
I know you are doing this with a purpose but take care. Any diet beyond just eating sensibly is fucking stupid/dangerous and categorically WILL fuck you up in some way. Anyone who says otherwise is selling something.
Yeah im not legitimately going to do the mental ones, but my goal is that if there really is any worth to the ones that aren't so mental, such as you suggested the Atkins diet, im never going to do the ones such as salt and pepper, i know that just drinking pepper and water will completely make you go arse over heals, so i wont be doing that. I mostly asked about mental ones as i am going to be interviewing a nutritionist and a dietician about what effects would these so called "diets" really have on us, i will be taking part in some of the diets for experiment wise, such as is this diet better than healthy eating and exercise, but of course the ones that will really screw me up, no not a hope in hell, even if this documentary might go places im not screwing myself up just for that.