I've had several.
At about 19 years old, I went to a party in a nearby rural town. Driving home late at night (and after having had probably more to drink than I should have and still been driving) I was going along one of those windy rural roads when someone screamed "Stop!". Problem was that I was alone in the car. So I stopped. It was very dark and after I caught my bearings and adjusted my eyes to the darkness I realized that the road was going to curve up ahead, which I did not know, and so I would have continued going straight which would have put me off the road and into a small river.
My DMIL died in December. The next fall, we did a bunch of yardwork, and it was my job to take all the clippings and such to the dump to put in the compost area. The compost area was a large area walled in on 3 sides by a concrete wall, with the other side open so you could back your car up to it to dump out your stuff. So I get there one morning, and the compost area is completely empty except for a gardenia bush sitting in a pot in the middle of this big walled-in space. My DMIL's favorite plant was a gardenia. So I took it, because as soon as I saw it, I "knew" it was from her. I brought it home, told my DH the story, he thought I was a kook, told me that since the gardenia had been sitting out in the freezing cold November day that it was probably going to die. He continued to make fun of me for being a kook until the next Mother's Day, when that gardenia flowered.
My late DFIL loved pansies. He & I were very close. Every spring to this day (he's been gone 8 years) I get pansies randomly growing in weird places...I never plant pansies, but I have had them sprout up out of a crack in the sidewalk, in a flower box that was filled with dirt but I had put nothing else into it, under a random bush in the yard. I always tell my DH that his father sends me flowers every year.
The night after we put Ted down, I felt him jumped on the bed and lay on my feet for about 10 minutes. DH actually felt that one too.
I've got a million of these things. I think stuff like this happens more than we think, and if we are open to it, we would realize it. And truthfully, IRL I am a pretty logical, sensible person, not too much of a drama queen...but I have always felt like the people who love us don't leave us...they are just sort of on a different "plane" or something...