I'm surprised nobody's mentioned Areis yet. My first playthough many moons ago, I wasted countless hours levelling her up and working through her limit breaks. When Sephiroth gutted her like a fish, I didn't cry...I went into a fit of rage over the time I spent making her not suck. Every time I've gone through the game again, I never use Aeris once until I fight Lost Number in the Shinra Mansion, as in that fight she's actually pretty useful.
Also, Edward from FFIV...I mean seriously has there ever been a videogame character that's more of a pussy than Edward? "Oh noes! I took one hp of damage!" *hides off screen* *Boss laughs at his cowardice, rapes rest of team* "Hey, I'm back...oh shit" *dies*. Every fight with Edward in my team usually had two people fighting enemies/bosses, and the other one killing Edward...the stupid fucking spoony bard
Raiden's a given, especially seeing as Benji already mentioned the biggest hatred I have of him...other than the whole effeminate thing.