Here's the best rundown I've seen of the upcoming Rule 5 draft so far, and here's a long list of players teams protected. Based on what I've seen, the player I want, and a player I think Neal Huntington will give serious consideration if the player is available, is Rays reliever Eduardo Morlan.
Keep in mind that I'm no expert on most of these minor leaguers; I've seen clips of some of them and read up on all of them, but that's all. Also, I'm relying on USS Mariner's list and a couple other sources; I didn't go hunting for other Rule 5-eligible players I hadn't heard about elsewhere.
Obviously, what the Pirates need most is everyday players and starting pitchers. But everyday players are very difficult to take in the Rule 5 draft, because the best ones are nearly always protected and because in order to keep a Rule 5 pick, he has to stay on your 25-man roster the entire year (unless he gets hurt or fake-hurt, in which case you can stash him on the DL or in the minors for a while). It's very difficult to stash an unready player on your bench for an entire year, unless he's exceptionally versatile or nicely complements a player you already have. Of course it's possible a team would leave a very talented and nearly-ready position player unprotected but, Dave Littlefield aside, this rarely happens.
This year, the best position player available that I've seen is catcher James Skelton of the Tigers. He's worth considering because he's not old and he looks like he might become a plus hitter if he stays behind the plate, but his defense is apparently not very good, and he's pretty small, so his power may not come along. Also, he's a lefty, so he wouldn't really complement Ryan Doumit. First baseman Kala Ka'aihue of the Braves is another possibility--he showed great control of the strike zone as a 23-year-old at Class AA this year, but he probably doesn't hit for enough power, and it's hard to hide a first baseman for an entire year.
Pitchers are a different story, because a flawed pitcher might be able to have success in a major league bullpen. Starting pitchers can be good picks because you can stash them in your bullpen; this is what the Twins did with Johan Santana, for example.
The most interesting starting pitchers I've seen so far are Chuck Lofgren of the Indians and Donald Veal of the Cubs. They're both pretty rough--former top prospects who have flopped as they've moved up the chain. Lofgren had a disaster of a year at Class AA Akron. The Indians are having him relieve in the Arizona Fall League, and that has gone terribly, as he now has a 32.14 ERA there, with 18 walks against six strikeouts. I'd only want the Pirates to take him if their scouts spotted something they thought could be fixed, and even then I doubt it's worth it; Lofgren doesn't have blow-away stuff (though his curveball isn't bad) and may have succeeded at the lower levels in part because he was craftier than the hitters he was facing. Given his problems finding the strike zone this year, I don't think I'd want the Pirates to mess with him.
Veal, too, has control problems--his walks went from bad to worse as he repeated Class AA in 2008. Like Lofgren, he has struggled mightily as a reliever in the AFL. Also like Lofgren, his fastball is decent but not great, but he has a good curveball. One potential advantage is that Veal is apparently a pretty bright guy who might be able to make adjustments if placed in a big league bullpen, but his mechanics sound like they're a house of cards:
Well, number one was trusting my stuff. Some of my pitching coaches used to say, "Just trust your stuff and don't try to overdo 'cause you've got plenty. You don't need to do more than you're capable of."
And then number two is just slowing myself down. Sometimes I rush to the plate . . . if I get a couple of quick outs, I'll start rushing to get that last out real fast--getting ahead of myself. Then, once I start rushing, everything gets out of whack from the very beginning.
Again, if the Pirates' scouts see something about Veal they think can be fixed, great. But if not, I'd avoid him.
That leaves relievers, and of those, the one I like the best by far is Morlan. You may remember that the Rays acquired Morlan from the Twins in the Delmon Young / Matt Garza deal. He put up Playstation numbers in the low minors in 2006 and 2007, then held his own in Class AA this year. (And his numbers might have been even better if he hadn't struggled with shoulder issues early in the season; he was terrific down the stretch.) He's also been dynamite so far in Puerto Rico winter ball. He also has good enough stuff to be a valuable reliever, and he may be good enough to contribute right away. There's a decent chance he'd stick the entire year.