Bicycle helmets.

If you look at actual testing which is specified in standard for bike helmets... 1.2m fall onto a hemisphere. 2m fall onto a flat anvil. No tests whatsoever for sliding impacts, rotational brain injury (which is extremely dangerous), neck injury, or anything of this sort. Not to mention unrealistically rigid models of head. For all the standard cares, you can produce bike helmet which simply shatters into pieces at >2m fall speeds, which cracks into pieces when deformed even half as much as head could be deformed without serious damage (you'd be surprised, but bones are quite elastic), with high friction outer lining, so that in a sliding impact it gets you the worst rotational brain injury possible. And you could still legally sell this shit as "bicycle helmet"!

Those helmets are barely rated for pedestrian accidents, for god's sake, like walking into a streetlamp pole, or falling on ice (but not falling on stairs). This is frigging ridiculous. Why won't they get pedestrians to wear those helmets? After all, pedestrian brain injuries are more numerous.

If you believe that these barely-pedestrian-grade helmets are any better for cyclists than no helmet at all, well that's your own dangerous original research, the regulations and standards clearly do not provision for any testing to ensure that bicycle helmets are useful for cyclists.
You can do it all you like, then you'd better also wear the helmet when you're not on bicycle. Anyway, why "bicycle helmet" laws? Why not construction grade hardhats? Those also got some standards, similarly irrelevant to reality of bike accidents. I'd bet an industry grade hardhat has better sliding performance.

Bicycle helmet laws were lobbied by the Industry of Useless Things, simple as that, and so were the standards. IMO any useful bicycle helmet standard that would test for realistic accidents, with considerations for the total injury (impact, rotational, and neck), would only be passable by motorcycle style helmets, and nobody wants to wear those on bicycle.

And even all the uselessness aside, adults should be free to endanger themselves as much as they want when it does not endanger anyone else; motorcycle helmets should not be mandatory either. Not wearing a helmet on motorcycle may put you in more danger, but puts everyone else in (very slightly) less danger (you have larger field of vision without helmet, plus in the unlikely case of collision of your head with someone else, that someone else gets less damage if you don't have helmet) - it is your choice to make - I would recommend wearing motorcycle helmet, though I would not wear it on bicycle because it'd look too ridiculous.