It depends a lot on the girls' age,
My older girls always seem to want the glitter headbands, like Jenny Finch's. Or streamers with bling or zebra, cheetah, etc. Anything showy!
My younger girls seem to like the ponytail streamers. I've made some with only 3 ribbons, others with up to 7 or 8, just depends on the girl and the length of her hair sometimes. I've cut the ribbons shorter for girls with short hair as well.
All are made without any metal, and can be worn comfortably under both batting helmets or a catcher's helmet as well as a visor.
Poofy boutique or that kind of bow mostly don't work. Even if you put it on a pony-o, it will get pulled down or out of her hair when she takes her batting helmet off, due to it's size.