I've seen all the Space Shuttles in their retirement. It took me 10 years to get to them all.

But I saw Endeavor when it was still just on the ground (like Discovery). I can't wait to go back and (re)complete my collection!

Interestingly, with this display, you can now see the shuttle in all operating modes:

Endeavor is in launch configuration, Atlantis is in orbit configuration, and Discovery is in landing configuration. And if you count Independence at JSC, you can see it in transport configuration.