As I've stated before, I'm not a fan of the chainsaw as an anti-zombie weapon. But I am intrigued by this variant: a small chainsaw mounted on a semi-automatic rifle as a bayonet.
[Video Link] It would make the rifle absurdly heavy, but it would also provide some safety in the event that a zombie gets within four or five feet -- when the rifle would become ineffective.
It'll be years before I get a gun, largely because of the start-up costs (e.g. rifle, training, ammunition, gun safe), but I still have my lustful eyes on the Marlin 1894c .357/.38. And I'm coming to think that it would actually a better anti-zombie weapon than the Max Brooks-endorsed M1 Carbine. Why? Just try finding .30 carbine ammo in a sporting goods store. If you take a chance and smash your way into a sporting goods store in a zombie-infested town, you have a lot better chance of finding .38 ammunition than .30 carbine.
But, of course, I am still an armchair rifleman and am only speculating.
Hat tip to Confederate Yankee via Ace.