Surely I'm the most dangerous thing you could see.
But the truth is you could never live without me.
I keep it simple, inside I'm mostly just one character.
Half the time you don't even notice or care.
I help you look but you could never view me actually.
Mistake one letter and you might decide I'm not girly.
Just one hint twice for the true gumSHOEs: There can ONLY be one.
Edit: Ignore the hint if you're getting distracted by it.