I used to have the daggar blade with the round-hole guard on the top, that was used in the movie Terminator 2. I bought it because it was a neat looking knife, and was at a very cheap price.
I ended up selling it, at a profit, as it really had no practical purpose, and I like to carry my knives.
If a knife is made just for a movie, and is more of a prop, than usable tool, I won't really consider, unless it's a "Lord of the Rings" sword that will just be mounted on a wall.
Now, if I see a cool production piece, or usable custom/mid-tech knife that I like, I would consider it, especially if it's in a movie, or TV show that I really like.
Maybe if I had disposable income, I'd be more inclined to buy props.