I lived in a house surrounded by sand dunes, at the edge of a deep blue river. There was a cliff at the river banks, soft and plump with vividly gold sand, shifty, dangerous.
In a dream-within-the-dream, I fell asleep on the couch and dreamed that my mother was visiting, and she and I went out walking by the cliff. After awhile, "you're dreaming" came into my mind and I started dreaming lucidly.
The first thing I thought to do was push my mother over the cliff. I did it, and was pleased and amused that I had, but my dreamscape returned to the same scene twice more. I pushed her again the second time, and on the third I decided to use dream power - will her over the cliff without touching her pudgy flesh. She staggered towards the edge, but resisted, I said to myself, "c'mon, a li-i-ittle more," mentally coaxing her and focussing, and sure enough she dove over the edge with a scream.