Pete Best's mother won the money to buy her house where she'd open the Casbah Club in Liverpool betting on a horse called "Never Say Die"; a long shot of 30 to 1 or so odds. The club opened in 1959, that's where John Lennon, Paul McCartney and George Harrison met Pete Best, and Best became their drummer and the Casbah Club was actually where they played together even before the Cavern Club. Two major events from that minor, minor thing: one, the Beatles don't end up playing a major venue in their early days, and two, Pete Best doesn't meet John, Paul and George, and doesn't become a drummer in the band. For want of one bet on one horse, that all changes.
The Casbah Club doesn't just affect the Beatles. The Casbah Club was huge, and all the major Liverpool acts played there and it gave a venue for the new bands. They could play there, and if they didn't do so great they could rehearse and come back and play again and when the crowd loved them, they'd get more bookings. So without it, you affect all those bands that rose to great heights in Liverpool and affect the scene in Liverpool, and obviously many of those bands made it big in England and in the world.
Goes to show even the smallest thing, like sneezing or losing a pencil, could affect history.