Most notable one was probably Grubwithus (meet people over meals) -> GOAT (sneakers marketplace, valued at $3.7B)
Zimride (college carpool) → Lyft Grubwithus (shared meals) → GOAT Meerkat (Twitter livestream) → Houseparty Fates Forever (iPad MOBA game) → Discord The Lobby (finance recruiting) → Nuvocargo
Zimride to Lyft isn't much of a pivot, they're basically kinda the same thing.
That said, I'd say going from a SaaS model where you charge companies or universities $40k/year to access software that they provide free to students/workers is very different from a mobile app that does real-time dispatch / pickup inside a city and you charge the consumer directly. Different customer, different business model, different offering.