Well, this is interesting...per the Twittersphere, the Rangers have claimed LHP John Gaub off of waivers.
John Gaub is 27 years old, and was a 21st round draft pick of the Cleveland Indians in 2006. He was sent to the Cubs by the Indians on New Year's Eve, 2008, as part of the package for Mark DeRosa, and was claimed off of waivers by the Tampa Bay Rays at the beginning of this season.
Gaub only has 4 games of major league experience, totaling 2.2 innings pitched, all while with the Cubs. He's a reliever who walks a lot of guys (5.8 BB/9 in his minor league career) and strikes out a lot of guys (12.5 K/9 in his minor league career). Interestingly, for a pitcher who allows so many walks, he doesn't hit guys, having only 5 HBP in 229.1 minor league innings.
You can read this write-up on Gaub from the "Cubs Vine Line Blog" at mlb.com, which talks about his repertoire (93-95 mph fastball that can touch 97 mph, a slider and a curveball) and his history of shoulder surgeries.
Gaub could be an option as a lefthander in the bullpen at some point this season. Gaub is on his final option, which means after 2012, he has to stick in the majors or be exposed to waivers. I suspect he'll go to the Round Rock bullpen.