It just came to me, like a bolt from the blue.
The ultimate anti-zombie device is not a chainsaw (rather too heavy) or a flamethrower (cool, but indiscriminate) or even a trusty katana (although being the only weapon I am actually vaguely trained to use in any way/have in the house, it’s what I’d use) but a maggot-thrower.
If maggots only eat dead flesh, they are the ultimate anti-zombie device. You don’t have to worry about innocent living humans getting caught in it–sure, they’d be a little squicked by the sudden rain of maggots from your Mk III High-Power Maggot-Cannon, but they’d recover.
If the maggot-thrower couldn’t hold sufficient ammo (we’d need to conduct studies on how many liters of maggots to zombie are required) we could always go back to the old-fashioned method–suspect vats of maggots from the ceiling of the mall, dump them upon the invaders. Again, safe for humans, but death to zombies!
Come to think of it, in many climates with an active fly population, wouldn’t they lay eggs in the zombies and eat them all eventually anyway? Ultimately a zombie apocalypse would have to be self-limiting due to all the scavengers–sure, they might fend off vultures and so forth, but the little wee buggers? Nahh. Sure, I’ll grant you that in cold climates, you can have your ice zombies, possibly your mummified desert zombies, maybe–at a stretch–your salt-preserved coastal zombies. (“….arrrrrr….braaaaains….”) but in most of the world, zombiekind could really only be a temporary plague.