On the very rare occasion that my parents and grandmother are out of the house... I don't really do anything that I wouldn't normally do. Like everyone else, I blast my music and sing really loud but I do that in the car all the time. I may sneak down to the downstairs computers so I can use the scanner or something too, but that's about it.
Now that I can almost legally drive friends, I've been sneaking my sister in the car with me and taking her to the store while my parents are out. See, she somehow always has money, so I need her to come along! XD