You know what they say. Teach a man to be a Dungeon Master, and you can sell him modules and supplements for years; show a man enough cool tricks, and he'll be able to make new ones for himself, at home, for nothing, with only a small aubergine.
Take martial arts and fighting styles. Sure, Marvel Super Heroes had "Martial arts A" and "Martial arts E" and all that, and it was kind of okay, I guess?.. But not too exciting.
I didn't think much about it because I didn't know there was anything that could be done to make fighting styles more interesting.
And then came Zak.
"Here, have Lucky Number kung fu", he said. And it was simple (the simplest, in fact, that Zak could think of), it was fun, it was definitely bringing something new to the table. It left me in the position of a monkey who had just picked up a really cool stick - I like it, I can do stuff with it that I couldn't have done before, and I have absolutely no idea how to make another one like this. But who cares - check out my cool stick!
Then Zak said "Hey, have some more fighting styles" (The Lucky Number, because it works, and five more, equally simple and fun). And my monkey was even happier, but also started thinking. When you have six fighting styles, you start asking yourself: What if you use this one against that one? How do they work against each other? How do they work together?
It's a funny thing - knowing that there can be several very different styles in your game. You start looking for new stuff. I picked some moves from Xena Warrior Princess (the show and the RPG, it's an oldie but it's fun), and one interesting style from "Veins of the Earth", which was a fun book, though its authors, Patrick Stuart and Scrap Princess, later behaved like shameless lying abusers.
And then Zak said "Hey, buy Cube World #37 in The Store, it's got The Assassin's Opera", and this time it was slightly different, because there was more than just different fighting styles - each of the Assassins had his or her own appearance, stats and weapons. And their styles tied in with what they were, looked like, and used.
Cool, I thought. I was just assembling a group of female brigands for my players to run into, and I wanted each woman to have her own style and special abilities.
And I used a couple of Zak's styles, and the rest I just invented as I looked at the figures I had ready. It turned out to be really easy. Look at her, imagine what could she do to gain an advantage, translate it into game mechanics. Done, next.
I still use Zak's kung fu now and then, because being able to invent something doesn't mean you shouldn't use the cool stuff that someone else invented for you. In fact, it's even more fun this way.