watch out for snakes.
This one didn't really get started until I was in High School, which is odd because I grew up out between fields where snakes showed up in the yard all of the time. But later, at this time, we moved to a new town and into a development. Sometimes we would still see snakes in the yard but very rarely. But it became something that my dad would say every time we walked out the door, like a mother yelling, "Be careful!" or "Be back before dark!", but father would always yell, "Watch out for snakes!" at the last second as you walked out of the door. It was something that always made me smile as I was walking out of the door.
Later, as I was in college and my parents moved back out to open fields again, my dad was cleaning up the driveway and saw a large black snake. As my dad has declared war on snakes for as long as I can remember, he killed it with a shovel. He thought to himself that it might smell and stink up his property - we can't have that. So he picked it up in his gloved hands and tossed it across the street into a pasture surrounded by some very small woods. He tossed a little too high and the snake's corpse caught on a tree branch and wrapped itself around at least twice over 20 feet in the air! The snake remained there and served as my father's reminder to "watch out for snakes".