There's a superstition that if you change a horse's name, the horse won't work out. I hope it's wrong. Here are some names that I've changed.
Toonie (too much like loonie 'toons) became Suzie / Intuition
Liam became Oliver Sudden
Molly stayed Molly because, well, she's a Molly
Roan Pony (really?) became Smartie Pants because he was so darn smart (I rode him bridleless)
Sunny stayed Sunny for his personality
Dakota (a very flashy palomino) became Flash
Rebell (mis-spelled and he wasn't one) became Robbie
Ali stayed Ali because he knew his name
Daisy (I'd already had one) became Moxie because she's skookum like a dump truck
Misty (too much Marguerite Henry) became Mindy
Lightning is still Lightning but not the bolting kind, thank goodness
Freedom (blech!) became Shorty because he was short :)
Apollo (handsome, yes, a god, no) became Tucson because he was too fancy for Two Socks
and most recently,
Choctaw became Chocolate because he's sweet and one-of-a-kind.