Sand Hills
Cypress Point
Olympic Club
LACC North
Pacific Dunes
Medinah #3
Pinehurst #2
Shoreacres
Chicago Golf
Olympia Fields North

This is a very interesting exercize.  The list that this thread elicits is a neck scratcher.  Sosme of the courses named  make me shudder.Of course, I don't know what courses respondents have not played, but some of the lists simply show the futility to come up with a definitve ranking of "the best."
In actuality GW, Golf, and GD do a pretty good job.

In no particular order:
Oak Valley -- Beaumont, California
Rancho Santa Fe CC -- Rancho Santa Fe, California
Pauma Valley -- Pauma Valley, California
Pinehurst #2
Riviera CC
Pebble Beach
North Ranch CC -- Westlake Village, California (sentimental reasons)
Hillcrest CC -- Los Angeles, California (sentimental reasons)
Stevinson Ranch -- Stevinson, California
Rustic Canyon -- Moorpark, California
Golf Club of California -- Fallbrook, California
Oakmont CC -- Glendale, California
I guess that's 12. :-)

It is good to see some of my SoCal fav's that don't get alot of press on your list. North Ranch(original 18) was my college home course at Pepperdine and it was always a favorite. Oak Valley was my weekend course, it was worth driving an hour south of my home in Glendale to play a public course of that quality. I lived across the street from Oakmont in Glendale for five years but never got to play it, classic old course.
I will give you a list of ten you didn't mention in So.Cal that I enjoyed:
El Caballero CC-Tarzana
Calabasas Park CC
Wood Ranch CC-Simi
Malibu CC
Palos Verdes CC
Rancho Park Muni
Marshall Canyon
Industry Hills-Ike
Sandpiper
Rancho San Marcos

Shame on you Sean - fancy not including Enniscrone in your list. I thought you were a fellow disciple. I'm doing 2 lists: one for quality of course, and one for fun - whilst Royal County Down is clearly a great course, I'm not sure I could play it on a regular basis given my wayward driving. Likewise, Perranporth could never be described as a 'great' course but it sure is fun to play.

Quality:

Royal County Down
Dornoch
Pebble Beach
Ballybunion (Old)
Royal St Georges
Turnberry
Sunningdale (Old)
St. Enodoc
Formby
Enniscrone

Fun:

St. Enodoc
Perranporth
Beau Desert
Boat of Garten
Carne
Machrihanish
Pennard
Dornoch
Ballybunion (Cashen)
Tralee

Little Big Ed

You cheater!  Fancy slapping down two lists.  Be a proper chap and get it down to only 10.  

I think its quite evident that I think a fun course is a quality course.  I might sneak in Enniscrone at some point - I need a few more plays.  I did have some concerns with a few long walks between greens and tees.  

Ciao