I've sensed things, but don't know if I've actually seen anything.
The summer after my grandfather died, I stayed with my grandmother. She had moved downstairs with her mom. The upper and lower level were two different dwellings. My cousin and I used to play upstairs. Anyway, one night I had a dream (I think). I was staying in a bedroom at the front of the house. The stairs for the second level were directly over this room. I heard substantial creaking on the stairs like someone walking up. In my dream? I got up, went outside and up the stairs. I went inside and through the house. At the back of the house was the bedroom my grandfather died in (he had cancer). I saw him sitting up in the bed. He motioned for me to come sit with him. I did, and he told me he loved me, and explained why he wasn't around anymore. I told him I knew about death. I was maybe 6 at the time. We talked for a while (I don't remember about what), and he told me to go back to bed and get some sleep.
The next day, my cousin and I went up there to play and that bed was messed up like someone had slept in it. It was always made up. By the way, the house door was locked as it was supposed to be. It was really weird.
Years later, my cousin's family had moved into the house and remodeled (no problems). One night while her parents were out of town, her boyfriend stayed overnight with her. She heard the hallway door slam hard (her room was upstairs). That door DOES NOT CLOSE AT ALL. Between the thick carpet and it not fitting properly into the door jamb, it was impossible. The rest of the night, she said she felt watched. She jokes that it was Uncle Monroe (my grandfather) showing his displeasure for her boyfriend being there with her parents away.

So maybe his spirit is still in the house. My husband said when we stayed with them for the first time after my son was born, he felt a presence standing next to him. He said it felt threatening (my GD was very protective). He said it stood there awhile and moved away in the direction of my son's playpen. Then moved to my side of the bed, and finally back to him. At this point it didn't feel AS threatening, but he said it was there all night. On ther other hand, I felt at peace. By the way, We stayed in the same room he died in. I didn't think about it until afterwards. Even now, when we visit, DH says he always feel the presence, but it's more focused on my son, now, and it feels protective-safe. He says he knows it's the same presence, because it "warns him" when we get there, but then leaves him alone. Odd.