A little research unearthed some interesting things. First the definition of what the screwball is from Baseball Reference, "A screwball is a "backwards curveball." When thrown by a righty, it breaks like a lefty curveball, and vice versa. This pitch was conjured up because hitters have an easier time hitting pitches that break in on them than those that fade away. Lefties would throw this against righties, and righties against lefties." Now that that's out of the way, some other notable screw pitchers were Fernando Venezuela and Mike Marshall. Some others include Mike Cuellar (?), Willie Hernandez (I'm too young for this), Tim McGraw (finally I know one), and possibly John Franco.
It is assumed that the pitch has been shelved because for one, it is a very dangerous pitch for the arm and can cause serious injuries if improperly thrown. And two, you can get by without it, so why take the risk. Well, that's no fun.
Some good screwball reading at The Pitching Professor explains the different types of screw, from backwards slider, to reverse curve, and even the reverse screwball if that makes any sense. It also talks of Mike Marshall being the best there ever was at the pitch, which may be true. However, Hubbell's famous strike out streak of five straight Hall of Famers (Ruth, Gehrig, Foxx, Simmons, Cronin) in the all-star game gives him a strong case too.
Despite all this fun reading, I was quite down, until I stumbled across a screwball driven Hardball Times article. There is tons of graphs and charts about Pitch f/x that i simply don't understand and don't have the time to.
More importantly (to me), it talks of Reds prospect Daniel Herrera, a modern day screwballer! He's made two big league outings and thrown a whopping 63 pitches in the show, but more importantly he tossed 20 screwballs. There's confusion as to whether they are change ups or screwballs, but who cares? Mike Marshall, now a pitching coach, says that a screwball can be thrown safely if properly taught, so I'm holding out hope that the screwy makes a resurgence because, simply, I think they are incredibly interesting and want to see what somebody can do if they master it. With today's exploding curveballs and unhittable sliders, it's time for a new sensation and this could very well be it. Best of luck to Herrera, I'll definitely be tuned into his next outing.