The above posts list the first items to go. But on the KX500, EVERYTHING is a wear item. And I mean EVERYTHING. I've replaced a cracked airbox, Baja Designs dual sport stuff (horn, horn mount, metal headlight bracket, blinker relay, headlight wiring connection, headlight, etc.) all from wear, not crash damage. My rear license plate and rear led light both broke from the vibration! Renthal fatbars cracked (Ok, so those might have ben a manufacturing defect). The radiator screens fall off because the mounting holes in the radiator's aluminum flanges have enlarged so much. The tank/radiator shrouds crack from the vibration.
I've had my crank aligned and all new bearings in the motor, so it's not an engine maintenance root cause.
I don't seem to be distributing fasteners all over the landscape like other folks, and I have not been using Loctite.
Oh yeah, one of the "fail" items right up there with the pipe mounts is that the chain grinds it's way through the subframe leg.