We'll Be Together Again +1.
That was the first one I heard, and I fell in love with it. Led me to the rest of Pat's work eventually.
WBTA is still my favorite, even though it's probably not the most representative or iconic of the full range of Martino's work, imho.
It's very laid back, very down tempo, but it has the coolest, heaviest, thick foggiest, late night, ready to drift off feel of any recording I've ever heard. It's just magical.
But if you just want a "greatest hits" type of CD, "Pat Martino Cream" is pretty cool too. You get "Sunny" and "Send in the Clowns" and a bunch of other great tunes. Can't miss. Sound samples here:
http://www.amazon.com/Cream-Pat-Martino/dp/B000005BF4