I don't have any current horses at the moment, so I'll do my past horses:
Spooky mcSpookerson! But always tries hard. Loves kids. She was my confidante when I needed a mane to cry in as a kid/early teenager. She is a very honest little girl. Oh, and a biiig showoff!!
Mr Ego. He was the boss of his paddock. Tallest horse on the ranch. Let you know when he wasn't impressed about something. You knew when you hit the right spot when scratching him, because he'd stretch out his neck and his upper lip would twitch
My friends and I did something like this with our favorite horses at the barn, comparing them to the typical people you'd see at a high school, and this is what we came up with:
Duke (the ex-stallion I used to ride): He's a HUGE horse without being very tall.. he stands about 16.1hh, but has the muscle mass of a Halter horse... so we decided he'd be the jock, the one who has a comb in his pocket "just in case," and is always showing off his muscles.
Maddie: she's a very pretty girl, and anorexic, I swear! She'd be the popular girl at school that cries if her nails got broken.
Dancer: the girl next door.
Robin: He was always trying to show off and ended up getting hurt (ever heard of a horse getting his lip caught and ripped on a trailer? No? Me neither, till this big boy came along!) Always looking for attention, so we figured he'd be the nerd that tries to be cool.
Beau Jest: Spotted Appy, he'd be the nerd that you'd find pushing his horn-rimmed glasses up when he peeks around from the computer