Hehe I've had some fun times desensitizing Sock...
Yoga ball: He's okay with it now and I can "play soccer" with him a bit under saddle, just working on adding speed. Once I can find the dang plug that is! He used to be absolutely terrified of the thing and would go straight up and back if it got anywhere near him. He looked like those cat gifs you see all over the internet where they disappear upwards into thin air!
Tarp: Okay with it now, and really the only time he WASN'T was when I had it all over him, up to his ears, and he stepped on the corner. That was IT. He tore around the arena for about 5 minutes straight even after it slipped off. I was bawling!!!
And he's been just fine with tarps since then as well!
Pool noodles: Enough said, but he can handle 'em!
Bells/noisy things attached to him: A little snorty at first, but soon jingling happily away once he figured out the noise was coming from him and not some jingly monster chasing him.
Cows/livestock: He just wanted to be friends!
Dragging things: Getting better! He is more wary when backing and dragging than going forward.
Turnstiles: Now this is some weird thingy that they apparently do in the extreme cowboy races, but it's a little PVC pipe turnstile that you have your horse push with his chest under saddle. It was not his favorite thing at first since the other half obviously moves as well when you're pushing!
Cars: We were doing great! Until the a-hole in the Cobra... But we'll get there again.
Altogether I'm pretty lucky to have a level headed horse, I think! It's pretty fun to think of things to desensitize him with. I doubt, like Nikkibella said, that anyone is going to chase us down the trail waving noodles (what a mental image!) but in reality, you aren't doing it to get them used to the noodles, or the yoga ball, or what have you. The way I see it, every victory with silly objects or even common ones is just another, "See? Mommy/Daddy TOLD you it was okay, NOW do you believe me?" so that when you inevitably come across something scary on the trail, they can hopefully go back to the "Mum knows best" mentality instead of fight or flight.
This is a fun thread! I can't wait to see some of the other ways people "torture" their horses into being brave!