Today I discovered from the fount of knowledge that is Wikipedia, about switch pitchers. While there are many switch hitters (a person who can hit both left and right) playing baseball today, It is incredibly rare for a pitcher to pitch with more than one hand.
According to Wikipedia the first switch pitcher in the major leagues is a ‘dead ball era’ player: Tony Mullane. He played without a glove so switching was very easy for him. Another two contemporary pitchers followed his lead (see switch pitcher page).
The only modern pitcher to pitch is the majors is Greg Harris, although he only pitched left in his penultimate game against the expos.
The last pitcher I read about is Pat Venditte, who is currently an active pitcher in the minor leagues. Pat has pitched switch his whole life and even prompted a rule to be created. The ‘Pat Venditte’ rule [8.01(f)] reads as follows:
A pitcher must indicate visually to the umpire-in-chief, the batter and any runners the hand with which he intends to pitch, which may be done by wearing his glove on the other hand while touching the pitcher’s plate. The pitcher is not permitted to pitch with the other hand until the batter is retired, the batter becomes a runner, the inning ends, the batter is substituted for by a pinch-hitter or the pitcher incurs an injury. In the event a pitcher switches pitching hands during an at-bat because he has suffered an injury, the pitcher may not, for the remainder of the game, pitch with the hand from which he has switched. The pitcher shall not be given the opportunity to throw any preparatory pitches after switching pitching hands. Any change of pitching hands must be indicated clearly to the umpire-in-chief
This rule weirdly makes a lot of sense.