Terry Adams, Britt Reames, and Jason Alfaro.
Alfaro got a handful of at-bats while playing for the Astros in 2004, but he's a mediocre minor league infielder in an organization that's now well-stocked with less mediocre minor league infielders who also are on the 40-man roster. It's very, very unlikely that Alfaro will ever play for the Pirates.
Adams and Reames, however, might wind up with the Pirates at some point. Adams has not pitched at all well since 2003 and wasn't a great player even before he started slipping, but he's a veteran, so the Pirates, who need right-handed bullpen help, might use him at some point.
Reames is slightly more intriguing. If you remember him, it's probably because he pitched for the Expos in 2001-2003, but he's spent the last two years in the A's system. He has had good strikeout rates in the minors and even sometimes in the majors, although he's never had a good ERA there. He can start or relieve. If the Pirates need bullpen help, he can potentially fill in for a while, be cheap, and not embarrass himself.