For once i have a colt that i am struggling to spook!!! He is not afraid of hardly anything. Tarps, rattlers, hobbles, loud noises, scary tractors, umbrellas etc. he is not afraid of. Any fun ideas i can do? He is by far the bravest 3 year old i have ever owned!

So why are you trying to spook him?

If he's overly desensitized I'd be worried about sensitivity.

If he's truly bold than leave him alone and use it your advantage training.

My thoughts too, why are you trying to spook him , Lol, my goodness if hes this level headed then leave him alone. Theres just some that are born this way

Having one that flips the blackout panic flight switch daily, I would kill to have something quiet. I agree, leave him alone and just let him go through the daily motions of life. There's no reason to WANT a horse to spook 

LOL, I agree, having a young horse thats level headed and dont try to freak out on stupid stuff would be awesome, I would always scratch my head when my young one would get spooked at his own shadow or when he would hit/slap themselve with his own tail, he tryed to duck out from under me because he saw his shadow while riding under some lights at an arena, silly guy and he did that alot untill he finally grew up some I know theres many that do this, but good grief!!! I did have one that was pretty level headed and he was a blast to ride and didnt look for any boogers to spook at. 

Ha! I had one like that, he'd peel out when his tail touched his back legs and try to run from his own shadow, which is pretty hard to unless you're in the dark or going in a direction he couldn't see it ??