I wouldn’t call those helmets. They seemed like ordinary superhero cowls but with an added fin. (For aerodynamics or just awesomeness?)
Got to mention Dyna-Man, the government-sponsored super in THE GOLDEN AGE: his costume includes a stylized, old-timey football helmet not as a mask (since he routinely brings it along, but isn’t wearing it, during public appearances when he makes a point of having no secret identity) and not for protection (since he’s a flying strongman with Superman-caliber durability, and it gets smashed to pieces by hits that can’t possibly injure him).
But for the novelty helmets – and the action figures with their distinctive helmets, and the billboards where he’s got the helmet on, and his knack for donning that helmet while announcing to a cheering crowd that he’ll take the fight to America’s enemies – it’s a great little bit of marketing.
The orginal Ant-Man always wore a helmet. (It seemed to be his device for communicating with ants.)
John W Wintergreen (Electra-Glide in Blue)
most of the Knightriders
The All-American from Astro City wore a stylized 1940s-style football uniform, with helmet.
The Blue Knight, a vigilante-type, also from Astro City, wore a riot gear-style helmet with the image of a skull showing in the face plate.
The Atomic Knights wore full suits of armor.
Moon Shadow wears a football helmet, too, but in his case, it’s definitely protective. He’d “wear” a tank, if Revenant would let him. 
(His future self has a slightly less goofy outfit.)
Captain Britain
I’d like to see the helmet for Modok.
When did he have a helmet? Hell, his original costume’s mask didn’t even cover the top of his head and his hair stuck out. His later costumes (the ones I’m familiar with anyway) looked pretty much like Batman’s cowl, just with no bat-ears (and different colors, obviously).
