Any cool way to give your number to a woman in a fast and effective way ?

I was wondering if you guys had any cool ways to leave your number to a woman in a situation where you had a light / quick connection but not the time / opportunity to chat enough to ask for her number in a proper way. Situations like : - Boarding out of a plane with a hostess - Biology test with a nurse - Waiting in a taxi rank - Etc.

Business cards ? Always have a small piece of paper and a pen on you ? Anything else ?

Thank you