Sometimes there's a penny around you - on the ground, on your desk, on your dashboard, on the floor of the bus - and this penny is showing 'tails.'

This is what's known as a 'bad penny.' As Big Black says, "It's just a bad penny; it'll always come back to you."

From what I've learned, the best thing to do with a bad penny is

1. Throw it out if it's in your space and there is no hope of converting it.
2. Pick it up and immediately toss it away in hopes it will become a good penny for someone else.

I recommend against ignoring and doing nothing about it.