well, we do already have a recent "essential book" thread... if that defends your case anymore.
A few DVD's that I find essential, and if I were to start over with my collection, I would keep.
True Astonishment - Paul Harris... Absolutely incredible set. Also includes just about all of my favorite effects from AOA as well.
The Trilogy/Andthensome - Dan And Dave Buck... Maybe doesn't fit your style? tricks don't have emotional hooks? Impractical? Nothing time and practice can fix. I personally feel Dan and Dave's Trilogy is incredible. People complain about their performance, but I see it like reading a book, they leave so much more up to your own creativity and interpretation when presenting their tricks. I know with their material on here more than any others, I've been able to make my own. And the sleights and ideas are priceless.
Wayne Houchin.... I've yet to be disappointed by any of his stuff. Fantastic teacher. You learn so much more than just the trick by watching his dvds.
Genesis - Andrei Jikh... I've been through so many sets, trying to get into cardistry, this is the only thus far to give me the necessary jump start.
The Manchurian Approach... won't talk about it, because I want to keep it for myself.
and more