Did you see the plane?
I didn't notice this until I got the Blu-ray.
This is the 1:01:00 mark. Josh Brolin's character was just gunned down by the Gunslinger. Richard Benjamin's character says "Oh my God", and the Gunslinger says "Draw".
The camera goes out to a wide shot, and Benjamin's character starts running. Look in the sky towards the left and you will see a plane flying across the sky from left to right.
It's not actually a Goof because this is in the "modern" world after all so there is probably still air traffic over the Delos Theme Park.
I just thought it was a neat detail. I've seen this movie many times, but never noticed the plane until I got the Blu-ray version.
That's what I love about Blu-ray. You really notice the details.