This happened a few years ago when I was 15 or 16. My grandma had been ill for the longest time and one morning she finally passed away. I was home by myself when I heard the news from my mom and I was just about to take a shower. Obviously I loved my grandma and was heartbroken when I found out. So I'm in the bathroom with the door closed and locked, and I'm in the shower crying when I hear it.
Mind you, I'm home alone, and we live in this huge three story house so there are stairs everywhere. I hear running footsteps coming from upstairs (I was on the second floor) and they stop right outside my bathroom door. For some reason I wasn't scared or felt threatened in any way when I got out of the shower.
I went to the door where someone knocked on the other side. And then I heard a voice say 'it's okay'. I stood there for a few minutes before I unlocked the door and opened it. Of course nothing was there but I till this day believe that was my grandma when she was younger. She was wheelchair bound before she died but I just had the strong feeling that it was her younger self telling me goodbye.