[Exolent[jNr]]

PHP Code:

#include <amxmodx>
#include <nvault>

new const gKnifeNames[][] = {
    "Knife 1",
    "Knife 2",
    "Knife 3"
};

#define TOTAL_KNIVES sizeof(gKnifeNames)

enum _:ModelViews {
    Model_View,
    Model_Player
};

new const gKnifeModels[TOTAL_KNIVES][ModelViews][] = {
    {"models/new/v_knife1.mdl", "models/new/p_knife1.mdl"},
    {"models/new/v_knife2.mdl", "models/new/p_knife2.mdl"},
    {"models/new/v_knife3.mdl", "models/new/p_knife3.mdl"}
};

new gMenuKnife;

public plugin_precache() {
    // precache all knife models
    for(new i = 0; i < TOTAL_KNIVES; i++) {
        precache_model(gKnifeModels[i][Model_View]);
        precache_model(gKnifeModels[i][Model_Player]);
    }
}

public plugin_init() {
    // create the menu
    gMenuKnife = menu_create("Select a knife:", "MenuKnife");
    
    // add a default in case players don't want custom
    menu_additem(gMenuKnife, "\yDefault", "-1");
    
    // add all custom knives
    new indexString[11];
    for(new i = 0; i < TOTAL_KNIVES; i++) {
        num_to_str(i, indexString, charsmax(indexString));
        
        menu_additem(gMenuKnife, gKnifeNames[i], indexString);
    }
}

public MenuKnife(id, menu, item) {
    if(item == MENU_EXIT) {
        return;
    }
    
    new _access, indexString[11], callback;
    menu_item_getinfo(menu, item, _access, indexString, charsmax(indexString), _, _, callback);
    
    // grab selected item
    new index = str_to_num(indexString);
    
    // check if chose default
    if(index == -1) {
        // set blank models so the default knife model is used
        SaveModels(id, CSW_KNIFE, "", "");
    } else {
        // save new models
        SaveModels(id, CSW_KNIFE, gKnifeModels[index][Model_View], gKnifeModels[index][Model_Player]);
    }
} 


Remember that those functions were made for multiple weapon support.
If you are making just a knife menu, these codes could be made a lot shorter.