War is hell, and sometimes the simple helmets worn to protect against a range of impacts are just not up to the job. This has led to the introduction of the Sandbag Helmet, which behaves in a similar manner to that of wearing a sandbag on your head.
It can do this because it has a double skin that allows the space in between the innner and outer layer to be filled with about 20lbs of sand. This makes it quite heavy, but a pair of fold-down padded wings allow the more substantial helmet to partly rest on the shoulders, relieving any potential neck strain.
Note: this idea is the combat variation of the head cooling helmet post featured in the link.-- xenzag, Oct 18 2018 A_20Cool_20Head [xenzag, Oct 18 2018] Clever. You could wear it as a regular hat when deflated and only fill it in a situation where comfort isn't top priority.-- doctorremulac3, Oct 18 2018 Could be filled with gunpowder too-- vfrackis, Oct 18 2018 You'd be surprised how many people still ride around wearing army helmets [+].-- 4and20, Oct 19 2018 random, halfbakery