A lot of the characters Kirby created for his solo books at DC and Marvel:
Shang Chi and the rest of the MoKF cast:
Tarr (or was he a pre-existing character, like Nayland Smith?)
Mantis, in Englehart's Avengers
the supporting cast in Gerber's Man-Thing series:
I always liked the idea behind Ulysses Bloodstone, but his stories were too scattered to get a handle on.