By Scootah:
"Okay, here I am, on WiFi BT, and... my U-Turn flinches?! Here's the battle
I send out Ambipom @ Wide Lens.
Trainer sends out Charizard
Ambipom uses Fake Out!
Charizard Flinches!
Ambipom uses U-Turn!
Switches to Sharpedo @ Razor Fang.
Charizard Flinches!
So... is this because the Sharpedo had razor fang, or can U-Turn flinch on it's own?"
Interesting, eh? Unlikely to be really helpful, but it's an interesting bit nonetheless. I guess if you switch to a Pokémon that is holding an item like that, then the opponent can still recieve the effects of the attacks.
This means, if it is true, that the game doesn't check the small chance of Razor Fang/King's Rock until after the attack has been executed. Same with other effects (like Sludge Bomb and Poison Status), I'd assume.