Oakland Athletics reliever Pat Venditte is a natural right-hander who throws a mid-80s fastball from both sides, along with a slider and occasional changeup, writes Howard Megdal in a 2014 profile of Venditte for Sports On Earth. Before missing most of the 2013 season with labrum surgery on his right shoulder, however, his right-handed fastball hit 94, says John Nalbone for the Times of Trenton (NJ).
The only website I know of that separates pitchers splits into both batter's handedness and pitcher's handedness is Minor League Central, which is important because Venditte does pitch at a platoon disadvantage whenever he faces a switch-hitter. For 2015, Venditte is pitching slightly better on his non-natural side, as a lefty:
|Pat Venditte 2015 minor league splits|
|v. L as LHP||40||12.0||4||0||1||12||0||1.45|
|v. R as RHP||63||14.0||12||1||8||14||1||4.06|
|v. L as RHP||8||2.0||0||0||2||2||0||4.2|
|v. R as LHP||20||5.0||3||0||2||5||0||4.06|
Unfortunately, before this year, it appears that minor league baseball did not keep careful track of when Venditte switched hands. Just eyeballing his year-by-year splits, however, he tends to strike out more left-handed batters. Here he is retiring San Francisco Giants right-handed batter Justin Maxwell on a ground ball and striking out left-handed batter Brandon Belt:
Happy Venditte Day.