This is a card that belongs in almost every gadget deck, and also in decks which have a draw structure that is not as likely to cheat in lowball.
The trait will allow you a persistent Hiding in the Shadows each turn which you can abuse to go into a fight confidently that your best fighter won't be immediately shut down via an easy Sun in Yer Eyes, and unlike the Peacemaker it doesn't deprive you of your dude's weapon slot, allowing you to boost that Flame-Thrower without fear.
All this makes even more sense for a weaker-structured deck since you actually need a decent stud bonus to make sure you can pull a decent shootout hand, something which a bullet reduction will harm badly.
However the most overlooked aspect of the Helmet is to scout what to expect from your opponent. Lose lowbal and don't know if you can take out your opponent? Check their hand to see if they're holding onto any Pistol Whips and so on. Don't see any cheating in their hand? Time to gun for those 5-of-a-kind at every opportunity.
If your opponent is smart, once you've scouted a play hand without cheatin', they'll start avoiding for the rest of the turn at least, so make sure to bully them as much as possible while you have the advantage.
The natural weakness of the card is its low value, making it a risk in a high-value gadget deck, such as one around Flamethrowers. However it's well worth the risk to run 2-3 of them anyway.
And if this sort of risk is not your cup of tea, you can switch instead to the low difficulty gadget suite of Mechanical Horse/Holy Wheel Gun/QUATERMAN/Telepathy Helmet which all conveniently share the same difficulty, allowing your Mad Scientist 2, such as the affordable Kyle Wagner to invent everything risk-free.