I've had a few.

When I was about ten, I was sitting on my grandma's kitchen counter. If I held my arm out, I could drop a rubber super-bounce ball, it would hit the linoleum with a loud "bap!" and would fly straight back up into my hand. After several drops, it fell but made no sound. We never found it.

When I was moving out of my parents' place, I was taking things out to the truck. Nobody else was home, and I was using the kitchen table as a middle ground between my room and the truck out back. I put a large, colorful lamp on the table, went back to my room, and it was gone when I returned. I looked everywhere, and made several cycles from room to table to truck, to table to room, to table to truck. I finally gave up, sat there, and stared at the spot where I'd put it. After a few minutes, I got up, went to my room, came back with something else, and the lamp was sitting on the table, exactly where I'd left it.

The third happened last year, and was the only one I saw happen. I got home from shopping, took a few oranges out of the bag, and brought them into my bedroom to eat while I worked. I tossed one onto my bed, and it hit the dark brown cover and appeared to go into it, as if it fell into water. I took the covers off, looked around and under, and never found it.