What are five low‑cost guerrilla marketing ideas you've tried and actually worked?

I recently saw a social post from a local museum. A guy was waving to the camera in front of the museum, and caption reads, “We are out of social ideas. Just come visit.“ It hit me like a charm and I was actually trying to identify the entrance of the museum in the short clips.

What examples have you encountered or come up with that actually work like this?

Handing out professional business cards and flyers at major events