Bob Gibson was a damn fine hitter as a pitcher. Gibby had 5 HR in a season twice in his career, and had a lifetime .206/.243/.301 line with 24 HR and 144 RBI. He was also a Harlem Globetrotter.
Bob Feller actually drew 100 walks and drove in 99 RBI and had 8 HR. Not too bad for a hurler.
Parisian Bob Caruthers was such a good hitter for the St. Louis Browns (Cardinals) back in the 1880s, that on days when he wasn't pitching he played RF. In 1886 he won 30 games for the Browns (who also won the World's Series that year) and had a 2.32 ERA, and also led the American Association in OBP (.448), OPS (.974) and OPS+ (201)!!!
His career pitching stats are 218-99 record, 2.83 ERA, 2828.2 IP, 310 GS, 298 CG, 24 SHO, 900 K, 1.158 WHIP, and a 122 ERA+. His batting line is: .282/.391/.400 in 2906 PA, 695 H, 104 2B, 50 3B, 29 HR and a 134 OPS+! He won 40 games twice, 30 once, 29 twice, 23 once and 18 in his last fine season. He hit over .300 twice (.334 in 1886 and .357 in 1887) and topped 100 hits 3 times. Doesn't sound like much now, but this was back when the seasons were only around 135 or so games long! Not bad for a hitting pitcher! He only played for parts of 9 seasons, unfortunately, and that keeps him out of being eligible for the Hall of Fame. However, I think an exception NEEDS to be made for Parisian Bob. After all, he was Babe Ruth before there even was a Babe Ruth!!!
Fernando Valenzuela was a decent hitting pitcher. Jason Marquis and Micah Owings have already been mentioned. Oh yeah, Brooks Kieschnick was a RP and PH for the Brewers for a few years not too long ago. Surprised he wasn't mentioned back when the thread started, that was closer to his time!
"It ain't braggin' if you can do it!" Dizzy Dean