What 1 helmet would be best for all around use ? ... There are multiple helmets specificly designed for a particular use but wanting to buy and keep track of only one what would folks here think best to have ... while a militia/combat mindset might lean towards a ballistic rated mil. surplus head protector, the more likely thing we are likely to need it for is from fall while walking on steep terrain, working in our own A.O. aftermath of a storm or earthquake, etc. ... helemts that come to mind ... bicycling helmet/ plastic shell not just the styrofoam - advantages light weight and low cost should offer decent protection from fall ... plastic "OSHA" helmets offer protection around construction sites from tools being dropped from upper floors depending on size of object dropped how much protection ... offers little/no protection at the base of skull where the spine meets ... DOT motorcycle, baseball, footbal helmet ussually fibreglass shell with padding inside offers better side and back of head protection but getting physically heavy to carry and hot to wear ... steel pot mil surp. helmet, was cheap ( $10 ) when phased out but are getting harder and more expensive protected troops for years altho they were designed more to deflect a bullet rather than stop a bullet ... current issue kevlar helmet here's ballistic protection expensive ( but as more wind up on surp. market are becomming more affordable) also heavy to carry and hot to wear but when you need protection these are hard to beat

You're kinda asking a lot from one helmet.
You wouldn't want to wear a GI helmet to work in attic when just a "bump" cap would work.
And you wouldn't want to wear just a bike helmet for working under linemen either.
Just like you wouldn't want just one knife.

try protech.com military ones 50 buck

Caving Helmet might be something you would be interested in. PETZEL Spelios Helmet with Duo Lamp. Im a Caver and these helmets have saved my skull several times and has light

http://www.moosejaw.com/moosejaw/shop/p ... 000001_-1_

I just picked up a PSGT helmet, with new insides and cover. I am quite happy with it, but it is good for only tow things, helping stop light rounds and shrapnel. Yet, thats all I expect out of it. Helmets, like all other tools, must be picked for the job you plan on doing.

Just get ya an old GI helmet. It was good enouth for WWII!