Effect
May make the foe flinch. (Hold)
So Razor Fang will give your attacks an additional 10% chance to make your opponent flinch - but only if you move first. If you have a Pokémon with wicked high speed and a strong contact move, this can be a good setup.
I'll be honest, the flinch rate feels pretty unreliable. Razor Fang is also how you evolve Gligar into Gliscor, just have Gligar hold it and level up at night. So if you're after a Gliscor, this is what you need. Thats going to be the main reason to use this item, IMO.
Game:Polished Crystal