What are some 'deep' oracle cards that you would recommend?

Luna's Crone

some of my choices that weren't already mentioned are:

The Spirit Messages by John Holland I love this one. i use it alot

Shamanic Healing by MIchelle A. Motuzas

The Halloween Oracle by Stacey DeMarco Its an everyday oracle not just for halloween

The journey oracle a new aquisition that i really like so far.
 

nightowlwoman

I think it was already mentioned but I highly recommend the Faeries Oracle by Jessica Macbeth and Brian Froud. It was the only deck I worked with for years and has been one of the most helpful and versatile.
 

EmpyreanKnight

I'm going to second the I Ching Holitzka - it is a marvelous oracle, especially if you pair it with one of the more magisterial I Ching books. It is not absolutely necessary though: the LWB that is included in the deck is very meaty too.

One day, I'm going to delve deeply into the system, and along with those triple brass coins with square holes in them that I previously purchased and my books, this oracle would be my close companion.