I'm not sure if the Pirates can even draft anyone, since their roster is, as far as I know, currently full, but if they drop someone soon and are allowed to pick anyone, here would be some of the guys I'd consider:
-Ben Julianel, Yankees: Left-handed reliever who strikes out a lot of batters. Stealing from the Yankees would be fun.
-Fabio Castro, White Sox: Castro is 5'8", so he's not a player the Pirates would ever take, but he struck out a batter an inning this year at Class High A Winston Salem, and he was only 20. Some other team will take him.
-Rafael Rodriguez, Angels: Right-handed reliever who pitched well in Class A last year at age 20 and throws very hard.
-Bob Zimmermann, Angels: Righty reliever who struck out more than a batter an inning last year in the tough High-A California League.
-Carlos Guevara, Reds: He hasn't been young for his levels, but he has just mowed hitters down everywhere he's gone. He missed time last year, but it was because of a groin injury, not arm problems. He struck out 14 batters per nine innings at Class A Dayton in 2004 and 11.4 last year at High-A Sarasota. Also, he throws a screwball. That's awesome. If I were the Pirates, I'd take this guy.
-David Shafer, Reds: Another potential reliever. He (basically) skipped a level this year and kept on getting batters out at Class AA.
-Brandon Sing, Cubs: A mediocre defender who nonetheless has power and patience - he had a 942 OPS at AA last year. I don't see the Pirates taking a flyer on him, though, especially since they already left Adam Boeve off the roster. I saw Sing play at Dayton in 2004 and thought his swing looked a little slow.
-Matt Chico, Diamondbacks: Put up a bad ERA at Class AA Tennessee this year, but his peripherals were still good, and he was only 22. He then got sent down to Class A+ Lancaster and pitched very well.
Of all these guys, I want Guevara on my team. He's something like the Reds' version of Josh Sharpless, and he could conceivably be an asset in a major-league bullpen next year.
I got these names from Rotoworld and looked up other information on my own.
If anyone wants to add anyone else they like, feel free. And just so you know, I'm no expert on any of these players, just a guy who Googles minor-leaguers in between bursts of actual work.