usefull potions:

Mega-potion of STR (I love these! I can out DD a BRD on my PLD by using them)
Mega-potion of INT
Mega-Ether
Hi-Potion and better
nerve drops
throat drops
maddening potion
Elixer
all the status inducing potions

there could be more, I just haven't used them. OP try them, you'll see potions are quite usefull.