FFXIII sports some of the most ridiculous names for characters I have seen in a long time.  As such my friends and I have decided to come up with better names for each character which we feel better fit the attitude and look of the character:
Lightning-->"Lightning" The "main character" if there is one.  Her name was surprisingly hard to change because it just seems to fit.  So we remained calling her Lightning with the occasional "Katie Holmes" thrown in to see how it fit.  Not very well unfortunately.  If you've got a good one post it!
Sazh-->"Shaft"  Who's the black private dick/ That's a sex machine to all the chicks?/ SHAFT!/ Ya damn right!    The female chocobos want him and the male chocobos want to be him.  The afro and the guns don't hurt either. 
Snow-->"Clay"  This just popped into my head when I first saw him.  Also how can snow play the tank role?  It's so easy to crush and melt and bend to your will.  Clay, on the otherhand, can take a pummeling and dish it back out.
Hope-->"Tad"  Really?  What kind of a name is Hope?  He is clearly from the Australian outback with a boomerang that FOLDS IN HALF!  When will he learn?  Don't fold boomerangs in two.  But if there's one thing he knows how to do it's rage-out.  Honestly, just watch him cast spells and you' ll see what I mean.  Thus he was affectionately called "Tadpole" and is still referred to as such in bouts of anger but this was shortened to "Tad" to those that know him well.
Vanille-->"Coco 'Shoopuf' Chanel"  Just feels right for someone that can't make up their mind about which accent they want to use.  
Fang-->"Kimahri"  Cause nobody cares about either of them and you hate it when you have to use them.  As well they look similar and both use the same weapons.  Damn Kimahri...
 
Did you refer to the characters by any other names?  List 'em!

they ask people with cats.

Funny post but I completely disagree with the Fang statement... Fang is one of the best characters to use (not to mention has the best voice) in a lot of situations... high dps, debuffer, tank and Highwind is the most overpowered move in the game. Whereas Kimahri really was useless.

Whenever I see Fang I always think Pain from FFX2 and Vanille's name  I always think is Penelo from FF12.  I like Sazh and Snow as names for those characters a lot.
 
As for Lightning, they explain that it is a code name she gave herself, you find out her real name towards the end of the game. Hope is also explained sort of. There is a reference of him acting like the meaning of his name.

Hope is a dumb name but "Tad" ?...really I think that is even worse.  they should just name the characters Steve, Bob, Jane etc...might as well lol

Hope and Snow are indeed dumb names but the other ones are fine.

" Hope --> As in: We hope people don't notice we recycled Vaan from FFXII. "

Fang is the character I control, I have made her to mad damage to mobs, and she has Bahamut which is always nice.

" they ask people with cats. "

"Vanille-->"Coco 'Shoopuf' Chanel" - I call her Ms. ICantMakeUpMyUselessMind because she can't decide whether to stick to Australian, or attempt to fake American "

 Fang-->"Kimahri"  - WTF is this? She's probably the BEST character to use in the game IMO. She's my strongest character right now.

Fang's actress blows my minds, for a person who isn't Australian she can keep an straight Australian accent better than Vanille.

Has there ever been a logically named character in Final Fantasy games?
 
Next protagonist will be called Thunder. I'm callin' it.
 
Hell, the way they choose names now, one could be called Racism and another could be called Whale Vagina.

still, none of them are anywhere near as bad as "Edge Maverick" from star ocean 4. 

If you aren't using Fang, I don't know what to say.  The character with the highest possible Strength stat, she is easily the best Commando you can possibly use.  Nevermind her Highwind ability.   

" @Aus_azn said:

"Vanille-->"Coco 'Shoopuf' Chanel" - I call her Ms. ICantMakeUpMyUselessMind because she can't decide whether to stick to Australian, or attempt to fake American "

I know, and guess what the actress that voices her is Australian!!! WTF?  

 Fang-->"Kimahri"  - WTF is this? She's probably the BEST character to use in the game IMO. She's my strongest character right now.

Fang's actress blows my minds, for a person who isn't Australian she can keep an straight Australian accent better than Vanille.

"

This thread has made me realize that more JRPGs should have Australians in them. They seem to make stuff slightly less lame.

I hope to high hell that you're not talking about Vanille.

Fang maybe?  I liked about 2/3rds of her dialogue.
 
Also I really like the accent.  Vanille just needed to shush most of the time.  Seriously half of her dialogue could be replaced with a head nod.

" Fang maybe?  I liked about 2/3rds of her dialogue.  Also I really like the accent.  Vanille just needed to shush most of the time.  Seriously half of her dialogue could be replaced with a head nod. "

Fang-->"Kimahri"  Cause nobody cares about either of them and you hate it when you have to use them.  As well they look similar and both use the same weapons.  Damn Kimahri..."
 
I use Fang in my battle party constantly. The other names are pretty apt, though. Well done.

Fang is awesome, I loved all her dialogue and she is IMO the most versatile character in the game. She has Mediguard as a Sentinel, she has Bravera and Faithra as a Synergist, has the highest DPS as a Commando, has a wide range of Saboteur skills (except Poison). The only thing she's lacking is the Magic power for a Ravager and Medic, but Hope's got me covered there.

" They put a retard in a bag and they make words out of the sounds they make when they hit the bag with bats, also that's how they wrote the story. "

Hope would have been acceptable, but they just had to go and fuck it up when Lightning said "you have to have hope" or whatever the hell.