Hmm... well, I'd have to say Versamark, Pallette Noir Black, the CS Pallette inks, Memento black.... then it depends on what I've got a need for after that. I've got so many ink pads I really shouldn't ever buy any more!!
I totally love the Fresco chalk ink pads for doing chalk look stamping.... these were the original chalk type pads, and since I have the reinkers for mine I hope to use them for many years to come.
Monica