What's the most creative customer acquisition strategy you've come across?

Uber's free rides program way back when they launched helped them become well-known, quickly. Within a few weeks, it seemed like everyone I knew was aware of them, and using their service - seemingly out of nowhere.

Free standalone tools often end with creative approaches to attract new customers

Offer Some free perks like telecom companies offer free internet data and minutes with every package they sell.

Even though it isn't creative. Applying a freemium pricing strategy was a good idea.