That's why you have the nail-gun on standby. The problem with pick-axes, crowbars, bats with nails in them, etc., -- is that for more decomposed zombies, that sharp edge is likely to get stuck or embedded. This would suck, because you would either lose your weapon, or be compromised trying to remove said weapon from said zombie. Based on my research, blunt objects (if used correctly), may be the best option. The reason I endorse the nail gun, is that your weapon is easily retracted. The bottom line is, if you need multiple blows to cave in a zombie melon, you need to head to the batting cages, and increase your bat-speed. I also have come up with a zombie-speed unit. Called the "estrada" abbreviated "JE"s -- basically 1 estrada is equivalent to 90 feet in 90 seconds. It will become essential for survival to know how many estradas the zombies are attacking at, to help select appropriate defense weapons. I don't think we should assume that "virus zombies" will attack slower or faster than "nuclear waste zombies". It would just be easier to say "Zombies heading your way, 4.5 JEs"