Here are some of my tips:
(1) Segregation. It has worked well for me. The number of times an poor user dips into the knice knives is very rare. And here is the kicker, in order to get some really good segregation you have to buy a lot of knives. Ok, maybe that isn't necessary, but it helps.
(2) Cheap Henkels or Victorinox paring knives. Relatives and in-laws rarely use the big knives, and will mostly go for paring knives.
(3) Wa Handles. Wa handles scream out "DO NOT USE". It's just how it is. And the prettier they are the lower the chance of unauthorized use.
(4) Instruction. By instructing the poor users, you have a win-win situation. If they listen, they might actually learn something, if they don't understand it and think you are a knife knerd then they will be even less inclined to use your blades. Just take out a strop, spray it with diamond spray, and talk about angles and stuff. They will never touch that sh!t again.
(5) Throw in a letter opener into the knife drawer. Just see if anyone uses it -- you'll be surprised and amused. Unless that is until they use your letter opener constantly to cut cheese, spread peanut butter, and on and on. Then you will be forced to label your letter opener because you are sick of people using it for food.
I'd post a picture of mine, but I don't see how to attach photos to this thread.