We used to have a little rat terrier that did trails with us. Hoovey is alright with big dogs, but little ones unsettle him. He doesn't spook, but does keep a really close eye on them.
His major spooking problem is when he trips, if he has no idea what he's tripped on. He'll do it sometimes when I'm leading him, as he likes to walk somewhat behind one of my legs. His leg will sometimes knock mine, and he comes up scared, does a little head toss and hop. If I'm firm with him and tell him what he tripped on, he's alright.
He also hates the porch swing in the front yard, and pieces of cloth on the tack rail (like rugs, shirts, etc.) They're sure to be horse-eaters!
"Sit tall in the saddle, hold your head up high. Keep your eyes fixed where the trail meets the sky. And live like you ain't afraid to die...don't be scared, jut enjoy the ride." - Chris LeDoux