Shooto (the fact that Shooto doesn't deserve a top spot on these kinds of lists anymore hurts my heart in a way few can understand): Hiromasa Ogikubo. He was the runner-up on the TUF: Champions season, a top-15 flyweight, and he holds a victory over Pantoja in the TUF house and deserved the decision against Tim Elliot. More people know of him than anyone else in Shooto right now. After that it's Tyson Osawa, who was on that TUF Japan show but lost against Mizuto Hirota in the quarter-finals.
Pancrase: Hatsu Hioki. Hioki getting KO'd got more notoriety than anything else Pancrase has been doing lately, including Hioki winning.
DEEP: I'd say Imanari. It's either him or Otsuka, since DEEP has no western presence so you have to go by what guys in DEEP have done bigger things, and Imanari has history behind him while Otsuka was a semi-finalist in the RIZIN tournament, which was pretty popular in America as far as things going on MMA-wise in Japan go. Imanari fought in ONE last, but he's still mainly with DEEP and I doubt his next fight won't be there, so, you know...
ZST (
@tinobar could answer this better than me): Shunichi Shimizu is probably more well-known in America than anyone else in ZST. He fought in the UFC, which I don't think anyone else in ZST can say, and he's been involved in some gif-able moments (like his back-side kick to the groin knockout loss in China) and has fought in Pancrase a lot, which is fairly popular on Fight Pass. Is anyone else more known in America fighting in ZST than that?