Smyslov - Engame Virtuoso
Lutz - Endgame Secrets
How to Play Chess Endgames - Karsten Muller
Dvoretsky's Endgame Manual 
Viktor Korchnoi - Practical Rook Endings

It's called "Die Endspieluniversität" in German, and the 3rd edition appeared there last year. No idea if there's a 3rd edition in English.

My choice is not very difficult:

André Chéron: Lehr- und Handbuch der Endspiele, 2nd edition (4 books)
Mark Dvoretzky: Dvoretzky's Endgame Manual, 3rd edition

Or if we count Chéron's masterpiece only as one book, I'd also choose:
Van Perlo: Van Perlo's endgame tactics
HH Staudte & Milu Milescu: Das 1x1 des Endspiels (preferrably 2nd edition since it has the nicest cover)
John Roycroft: The Chess Endgame Study (better known in the first edition title "Test Tube Chess")

Bowen, is that MacDonald's book?

I can say I prefer endgames books whose target
is the "practical player".

So my favourite endgames books are:

McDonald "Concise Chess Endings"
Pachman: "Chess Endings for the Practical Player"
Keres: Practical Chess Endings"
Howell: "Essential Chess Endings"
Seirawan: "Winning Chess Endings"

Good topic.

How to Play Endgames - Mueller
Van Perlo's Endgame Tactics
100 Endgames - de Villa
Understanding Endgames - Nunn
Endgame Virtuoso - Smyslov

Can I have 7?

Essential Chess Endings by James Howell
Practical Rook Endings by Edmar Mednis
100 Endgames you must know by Jezus de la Villa
Chess Endgame Training by Bernd Rosen
Fundamental Chess Endings by Karsten Muller and Frank Lamprecht
Endgame Tactics by Van Perlos
How to Play Chess Endings by Eugene Znosko-Borovsky

Great topic.

Müller and Lamprecht - Fundamental Chess Endings
Flear - Practical Endgame Play - Beyond The Basics
Karolyi and Aplin - Endgame Virtuoso Anatoly Karpov
Mihail Marin - Learn from the Legends
Van Perlo - Endgame Tactics

Honorable mention:
Rate Your Endgame is great but it loses it's value after you've gone through it the first time.
I like the Silman book a lot but it got kicked off the list by the others.
I also like the Beliavsky and Mikhalchishin three volume set a lot and Shereshevsky's two volume set that covers endgames based on openings but these took too much space to include on the list.

Some of these I've barely read though.  I'm starting to work more on my endgames now.

I forgot Capablanca's Best Chess Endings which is one of my favorite books.  I don't know where to include it on the list.  It's hard to kick off one of the other books because they are all so different and serve a different purpose for what I would want to study.  I think the Capablanca book is similar to Endgame Virtuoso Anatoly Karpov so maybe only one should be included.  It's very hard to leave Capablanca's Best Chess Endings off the list.