The most famous Border collie is probably Chaser, featured in a 2010 book by John W. Pilley called “Chaser: Unleashing the Power of the Dog-Human Bond.”
In the book, Pilley describes how he taught Chaser an extensive vocabulary of over 1,000 words. This made her famous in the animal cognition community, showing that dogs are capable of far more complex language understanding than was previously thought. The AKC adds that Chaser passed away in 2019 in South Carolina.