One of my cats does this with his toy mice. He only like certain mice (both color and style) and carries them from room to room to play. However, he usually puts them in his food bowl at night, then goes to bed. They are still there in the morning, then he takes them out to play again.

He also takes one particular red mouse (that's sort of beat up) and drops it in the water bowl. Sometimes he'll play with it in the bowl and/or scoop it out, other times he just leaves it to drown. He doesn't play with this mouse any other place other than drowning him in the water bowl. Crazy cat!!! But I love him.