Some 80 or so years prior to Caesar's assassination, a consul fomented a mob to kill a Tribune (G. Gracchus) who was pushing hard for land reforms. Historians often cite this as laying the foundation for the Roman revolution because it normalized violence as a political tool. It was followed by proscriptions and the Catilinarian conspiracy in 63 BCE.

What if Octavius never traveled to Hispania? Caesar may well have still adopted his nephew in order to make him his beneficiary. What would have happened if there were no Octavius? Possibly Marcus Antonius would have consolidated power.

Would we have no transistors today if Shockley hadn't worked at Bell Labs?

I guess my viewpoint strongly biases me towards seeing continuity and underlying processes. For every tipping point, there was a pre-existing process; for every process an event you can treat as a "handle".