Great, thanks James, now I'm feeling the pressure to come up with a list! 

Just kidding! 

I'm sure I'll think of more specific Cars later, but I'll put them into 6 categories…

1) International-only releases:

• Brian Park Motors

• Chuck "Choke" Cables

• Stu Bop (we used 3 Marco's for that scene, so who needs him!)

• Mini Adventures Chick Hicks with Trailer

• El Materdor

• Chase Paint Rollers & Tray (accessories that came with Luigi & Guido)

2) Store Exclusives:

• Target's Final Laps

• Target's Story Tellers

• Target's Black Friday 9-Pack (the 4 cars in the back)

• Wal-Mart's Mater's Secret Missions

• K-Mart's Rubber Tire Racers

• Toys "R" Us's Movie Doubles

3) Short-run items (at least seemingly):

• Fabulous Hudson Hornet (original version with Silver Rims)

• Fred (original large scale)

• Chuy

• Tokyo Mater with Oil Stains

• Shake 'n' Go Doc Hudson (once Fabulous Hudson Hornet came out, it completely replaced the normal Doc)

4) Items that Mattel forced us to buy multipacks to get, that not all could afford (or wanted to afford):

• Dalmation Mia & Tia

• Nurse Mia & Tia

• Mater the Greater Fans Mia & Tia

• Cannonball Mater (clean version)

• Aviator Mater

• Hank Hallsum

5) In general, Chase Cars

6) Finally, I have personally never found these at retail:

• Impound Wingo

• the last 4 to 8 Final Lap releases

• Shifty Drug Hauler

• Vinyl Toupee Hauler

• Paul Valdez (and if it wasn't for TJ Maxx & Marshall's, I would have never seen Chet Boxkaar, Oliver Lightload, and Ben Crankleshaft)

• Leland Turbo

• Mama Topolino

• Security Finn McMissile

• Sal Machiani

Don't forget about Supercharged Dinoco Helicopter — it was only released in Canada. 

Then there was the very short non-retail store run of Nitroade Crew Chief and Pittys box set in the US.  It was previously released in Canada.

Some others that are really rare (if we are including packaging) are WOC Lizzie, WOC Sally with Cone, and the WOC Sparemint 3-Pack (vertical package).

And of course, there's Impound Snot Rod with Confetti, for which just yesterday I received an offer of $400.00.

Fillmore1234 said:

Great post John! Completely forgot about the Mini Adventures Chick. Also, there were some American versions of Luigi and Guido with Paint Rollers and Bucket, but only a handful. You could even say that Lenticular Artie is just as rare since he was in the same Case.

I thought about the English card of that Chase package, but they were mainly found in Australia until some of the smaller retailers in the States started getting a few in. Good call on Artie too!

I've given up on Elmaterdor…

Brian Parks, Chuck cables and Stu I thought were easy to get in trade, non-us card of course

Your list is way beter John…BlueM go with his… 🙂

John in Missouri said:

As shown here:

 

Texas Tea Hummer

Hilarious and creepy and cool all at the same time

Regarding store exclusives, don't forget the K-Mart crew chiefs!