Fujin and Raijin
This pair can give you a lot of trouble if you're not careful.  For help about the first battle with the pair at the Balamb Hotel, look at the Guardian Forces page under Pandemona.  For the second battle with the pair in the Lunatic Pandora, use the usual method for fighting ie: one curer, one attacker and one indirect magic user.  Have your indirect magic use cast Triple on him/herself and then cast Regen, Haste, Protect on all the party.  You can also use Aura if you wish.  Have your curer cure whoever needs it whenever the need arises.  There is really nothing special for me to tell you for these battles.  Just work quickly and try to rely more on just attacking power (hope you have good weapons!).  If you have good weapons and high enough HP you should sail through this battle.  Just attack, if you can't manage that , use GFs and magic.
More information:
Getting your HP to 9999
Junctioning Magic
Magic List