What are some unusual proven growth hacks you saw to scale a startup?

We used to manage a website for a company that distributed customized wristbands (used at events, prisons, various facilities and functions). As a new business that has been built on eBay, they had no organic search presence. One of the features we built allowed people to request a free sample which would be posted out. One morning, the owner got on the phone with us super early, having been bombarded with thousands of requests for a free sample overnight. Turned out someone had put their website onto a forum that focused on sharing information about free stuff/samples companies were giving away. We froze the function and let users that had come from that site/referral URL know they were out of stock. A few days later, we noticed they ranked #2 on Google for "wristbands". Same thing happened again on a different forum a few weeks later and we saw the rankings go to #1. Those free sample sites had huge da and massive user numbers. Those inbound links were priceless.

One unusual tactic I've seen work is leveraging existing communities on platforms like Reddit to drive targeted traffic to a startup by providing genuine value and engaging content. Another is creating an exclusive beta user group that turns initial users into brand ambassadors, giving them a sense of ownership and spreading word-of-mouth.