Dear god, I thought I was the only one who didn’t find this funny at all. Until I saw his stupid face on a WoW commercial cashing in on it. It stopped being funny when it went from laughing at him, to laughing with him. He’s actually a dick in real life. Appeared on Fox and all. Anywho, sorry for the derail.
Hypocrite.
The HEV suit has a forcefield helmet that is invisible but protects the head from hazardous conditions (such as radiation, poisonous liquids, military engagements) should a regular helmet be missing.
It’s not science. It’s Science.
The HEV suits purpose is in the name. HAZARDOUS ENVIRONMENT SUIT. Just because that had purposes beyond it’s intended use doesn’t mean shit, a gunfight is still a hazardous environment.
As for the helmet. I think it’s implied he has one with him, we just don’t see him take it off/put it back on. Hence why he hasn’t died from radiation sickness. I think it is also implied that whilst headcrabs do attack him, he doesn’t actually let any near his head. The idea headcrabs only lunge at Gordon without coupling is idiotic, that is simply for gameplay purposes.
As someone so rightfully pointed out…
It’s a game.
Infact, scratch that thing about it having uses beyond its intended purpose.
The HEV suit had built in systems for handling weapons, for survey teams crossing over to Xen. So the fact it’s so good with dealing with gunfights, and the blunt trauma of projectiles hitting it is a given.
His chestplate contains a powerful bullet-magnet.
ive already explained this shit before, some one is running around with it in there signature
Looks in there
Oh, yeah, I see it!
he has big hands?
rofl u got me
So to say, HEV MARK IVb-upgraded model.
Ask Gabe 
https://tvtropes.org/pmwiki/pmwiki.php/Main/HyperspaceArsenal
His HEV suit is powered by TARDIS technology.
He doesn’t: A giant physics-defying wormhole in the shape of an inventory bar hovers slightly above his forehead. He and the bar-shaped wormhole have an intimate understanding and it lends him rocket launchers, guns, and ammunition when he requests it. Nobody says anything about it because it also eats people who acknowledge it.
Stick your dick a reality-bending anomaly and ye shall receive powerful friends indeed.