Who's This? The surgeon dude on page 27 of Who's Who volume V.
How you could have heard of him: To me, this character was always obscure and I wondered why he wasn't featured more in the Batman books. His shtick certainly fits his rogues' gallery very well. Doing a little research, I found that he WAS featured quite a lot in the 90s and 00s. He appeared in an episode of the Batman Animated Series (I'd forgotten), in Villains United and in several issues of Gail Simone's Birds of Prey. Of course, those later stories turned him into some kind of master torturer (sigh), which is very different take on the character. Maybe the version I'm gonna talk about HASN'T had any exposure in a long time.
Example story: Detective Comics #579 (1987) by Mike Barr and Norm Breyfogle. It's the next story AFTER where that Who's Who biography leaves off.
By the time the Crime Doctor was seen again, his hands were fine. Maybe Infinite Crisis fixed him. I have a feeling each Crisis Event restores him to health, gives him one more outing, only to be destroyed again. In that Birds of Prey story, he commits suicide to save his daughter from torture and murder. Time will tell if he returns to the New52, though given the darker state of things at DC these days, it would probably be more of the torturer version than the unethical healer of this and previous stories. Or perhaps the nasty female Crime Doctor that appeared in Manhunter, but that's a completely different character.
Who else? Between Colonel Future (our last entry) and the end of Who's Who volume V, relatively obscure characters included Forgotten Hero Congo Bill, though now Congorilla's been in a version of the Justice League. The Construct isn't exactly headline news, but you can't force me to read the one appearance I own - the Red Tornado mini-series (THE SHAME!!!). And there might have been Cyclotron, but his Who's Who entry came off a very recent appearance in All-Star Squadron, so at the time, not really obscure. So we'll move on to Volume VI, coming to a blog post near you in the near future!