When our Siamese cat died, years ago, I was devastated, but a few days later was in the bathroom putting my make up on, not even thinking of him or anything really at that particular moment, when I heard him meow. It was a meow in the house somewhere, not outside, and he had never been to that house as he stayed with my parents when I moved out. I like to think he came to let me know he was OK and to say goodbye.
My DF was the least woo person ever, but said he felt the cat jumping on the bed at night.
A few weeks after my dad died I was going in and out with buckets of water washing the car, again not thinking of him at that moment, when I smelt orange, like someone had just peeled one. Very intense for a minute or two then just faded away.