Castellan and Wolf Underling Familiars

There is one more that is 2x drop.

It is halloween kity cat, think it only came out once from gacha during 2011 halloween. It's extremely rare to the point it's existance is quastionable.

There is only one familiar in the data that's capable of casting the +100% Item Drop everywhere buff, and that's Wolf Underling. Neither of the kitties has an effect associated with them anyway.