Well, I wouldn't want to get a broom, but a Roomba? Happy camper. Any household-type gift that actually saves me work is a winner. Knick-knacks are NOT winners; I have issues with being unable to conquer clutter as it is, without adding items that don't at least have a practical use. (FWIW, I'll never forget the time my Dad got my mom an electric floor buffer. She LOVED that gift, because it meant she no longer had to get down on her knees to polish the hardwood floors. All of the jewelry he ever bought her paled in her eyes compared to that floor buffer, because it was luxury that made life easier for her every single week.)
As to things I really actively DON'T want (other than the knick-knacks), that would be scented products or anything having to do with coffee. I don't like getting headaches on Christmas morning.
A note about people who give something and say, "I saw it and it just reminded me of you." Really, say anything else, but don't say that unless the person is already gushing over the gift, because it's one of the biggest minefields on the planet, especially when the person you are giving it to is family. If it turns out that the item is something that the recipient would never in a million years choose to use, display or be fond of, that statement can make what is merely an unfortunate choice of gift actually hurt, because it sends a clear message that the person who bought it for you doesn't actually KNOW you at all.