There are a number of situations where a knife needs to be designed according to function. (Function being all the things an object can be used for outside its specific purpose)

The obvious examples being hunting, survival and combat knives.

Designing a survival knife will take some careful questioning of your client. You must find out what he is most likely to use it for and add 1001 other things on top. Survival and combat knives can be used as stabbing tool, pry bar, hammer, can opener, interrogation and intimidation implement, surgeon's scalpel, snake beheader, axe, fingernail cleaner and leopard stopper.
Your customer may have to use your knife only once, and if it fails, your client may end up extremely perforated by pieces of .223 or .308 diameter brass coated lead. In Africa, he might end up as leopard lunch, dinner and breakfast. It is not a responsibility to be taken lightly.

A large part of my customer base consists of hunters. Some with Rowland Ward size egos, and some with equally large bank accounts. Most are just plain nice people. They all have one thing a common: they want a chameleon called "hunting knife"
To design a hunting knife you again need to consider the possible functions of a knife. Bow hunters, trophy hunters, meat and biltong hunters, walk and stalk hunters, hunters who build a hide or blind, arctic, desert, forest and bushveld hunters all have a different set of requirements. You also need to consider the type of animal your client will be after and whether he will do the skinning and processing himself.

Thick skinned like eland and buffalo, thin skinned like deer and impala. Tons of meat to process like on a giraffe or walrus or a delicate caping job on a steenbok. Both the largest and smallest knives I have made were for Professional Hunters, the one to process giraffes, the other to cape small antelope.

Besides the obvious purpose of skinning and meat processing, a hunting knife may also be used for a huge variety of other functions. These can include cutting saplings to build a hide, food preparation, and repairing punctures on 4x4 tires, freeing spent cases stuck in rifle chambers and cutting bandages to plug up holes and tears left by an aggravated thorn tree.

As different as the uses and functions a hunting knife must fulfil, so are the tastes of hunters when it comes to choosing their favourite hunting knife.