Frank Difeo stands out for me too, but someone I don’t think gets any credit is David Hall, and here’s why he deserves credit.
At the start of the boom (1998 or thereabouts) there was really only one big online yo-yo store. Dave had been selling a few products on his very small site, but decided he wanted to go all in and offer an alternative (which became Skilltoys.com). When he started Skilltoys, Dave was contacted by the other big store owner who wanted to collude on yo-yo pricing, keeping them high and not offering any discounts. The store owner had been used to basically doing whatever he wanted, with no competition. Dave refused and not only undercut every price but also offered coupons and later rewards points to his customers. The big owner wasn’t happy with this, and actually struck deals with a couple of manufacturers who forced Dave to stop discounting their products, or they wouldn’t sell to him.
Even up to the end Dave wouldn’t be part of this price fixing, and it stopped him from carrying a few product lines that he would have otherwise. He deserves credit for ending a monopoly and bringing a choice of stores to the masses.