Well, I just didn't feel there was enough "I don't like bashing on people, but OMFGWTFLOLZBBQ!!!111 say away from (player)" threads yet... so I thought I'd take what I've learned from talking with others and first hand witnessed events of my own and compile together a list of those to avoid and just get it out of the way in one full swoop.
Anyways, those you should avoid include, but are not limited to, the following (the following names have been known to wipe out parties or claim to give someone a specific item only to give them nothing):
Aquarius
Ash Dragon
Aspidochelone
Baobhan Sith
Baronial Bat
Beryl-footed Molberry
Bloodtear Baldurf
Byakko
Despot
Enagakure
Faust
Fenrir Prime
Friar Rush
Genbu
Jormungand
Kirin
Nightmare Vase
Sea Horror
Seiryu
Steelfleece Baldarich
Suzaku
Tyrannic Tunnok
Tzee Xicu the Manifest
Ullikummi
Voluptuous Vivian
Wyvernpoacher Drachlox
Yensho
Za'Dha Adamantking
Zipacna
Well, that's what I got.... Some of these stories, I can speak of first hand, others are passed down from some rather reliable sources that I wouldn't normally discredit or chalk up as being falsified. If you wish to take your chances with these characters and judge them for yourself, so be it... and I wish you luck. Hopefully you can prove me wrong, but I know a good majority of the forementioned individuals have been known to wipe out entire parties as well as force players to waste time/gil for an item never given to the player wasting the time/gil. However, now you can never say you weren't warned...
Now that that has been said, can someone please pass the maple syrup?