I haven't finished reading the rest of the posts, 
but Yann is very right. . . a lot of people seem 
to be answering the question from their personal 
point of view -- which I'm having a ball reading! 
Don't get me wrong. ^_^

But I'm aiming to list anime so bad it just has 
no redeeming quality, "burn the masters to spare 
everyone else from having to see it" level of bad.

That is: "Junk Boy". I don't know if this thing 
even still exists, I can only pray it doesn't. 
The art was possibly the lowest grade you can 
imagine. The Kerroppi kids videos I've seen look 
like Clamp artwork compared to this thing. ^_^; I 
was lucky enough to be able to sell the tape to a 
used store, so I unfortunately can't provide 
screen captures of how bad it was. For the plot: 
Can you call a plot "bad" when there simply isn't 
one?? I've seen shows with poorly developed 
plots, slow plots, rushed plots, weak plots, and 
plotholes you could drive a Mack truck though, 
but this thing simply had NO plot. Unless you 
count it as having a repetative plot of watching 
the main character's erection lift anything in 
front of him every time any female walks past. 
(I'm not kidding. Those were truly stretch jeans 
the guy was wearing because he could flip over 
tables though them.) This show had NO redeeming 
value in any way whatsoever.

And before anyone asks, I have no idea why my 
husband brought this tape home. 9_9  But suffice 
to say, we now have a saying between us. When 
we're shopping for new anime and read the back of 
one that doesn't look too great, we put it back 
on the shelf with the comment: "Looks like a Junk 
Boy." ^_^;;

Many Sharp Smiles,
--Drac