the melee weapon is a last resort which is only of use if it allows you to extricate yourself and get back in shooting range distance. in such a situation..well..I'm not a fan of the Kanabo because it's heavy to lug around/run away with.. but a blade has less durability than a blunt instrument..so I'd keep a blade only for things for which I actually need a blade..like skinning, cutting etc etc..not for fighting. you can find sticks everywhere and bash some spikes in it to make it meaner.. a good blade? not so easy to come by...it's precious..you don't want to waste it by denting it on a rib, buckle or other hard object you encounter during a melee.. or by letting it get blunt through fighting tout court.
fatigue..again..if you're up against a couple of zombies you run and shoot them from a distance...or you can bash their head in with whatever weapon..if it takes you so long that you end up fatigued, you've got bigger problems.
if you're up against a horde and you can't for some reason run off..blunt instrument or weapon of lighter use...you're going down anyway