Weird Rattle Noise...

If you have the Weapon-R dragon intake like myself it could be that. As I am sure you noticed they do not fit very well with the dragon filter so what is happening with mine is that the top part of the filter is rubbing against the hood cover and it actually makes a funny sound like you have heard. Check your hood lining and see, and if you don't have one then check your hood lock because someone hit my car (one of many times) and actually pushed the front bumper down and I did not know and it pulled the lock down so much that my hood could not close (according to people an SUV backed up onto my bumper, my car was right under it and he just drove away and NO ONE bother to get his plate number or anything)
Hope my rambling helped or atleast gave you an idea of where to check.
GOOD LUCK

Damn, if anything it's probably relating the hood lock again, it seems a little loose, but I can't get it to create noise...car is all stock right now....

I've got a few mystery rattles also but most of mine sound inside, maybe one underneath the car (not the cat shield I already checked). None of my rattles are constant but some of the roads are so cracked up from earth quakes and plain sh*ty workmanship that sometimes they sound constant