Since Keenan McCardell was mentioned: 12th round draft pick. Of course there isn't even a 12th round anymore.
And since Christian Laettner was mentioned, apart from having been an All Star, he was also on the Olympic team.
Mike Piazza was a 61st round pick (allegedy only picked because he was Tommy LaSorda's godson).
Greg Maddux only won 20 games 2 times, but won 19 5 times and 18 twice.
Rickey Henderson arguably had a HoF career *after* breaking the all time stolen base record:
http://www.baseball-reference.com/h/henderi01.shtml
in 1990 Dennis Eckersley had more saves (48) than baserunners allowed (45). He had a .61 ERA/WHIP. Also might not be so surprising, but it's cool.
The Arizona Cardinals franchise has never won a playoff game. (lol, perhaps that's not so surprising). Until a few years ago the Saints were in that boat as well.
Tom Glavine has surrendered only 1 grand slam in 4300 innings. Mike Redmond is 21-48 against him (1075 OPS).
Charley " Old Hoss" Radbourne: In 1884 he pitched for the Providence Grays. They played 75 games. He started 73 of them, pitched a complete game in all of them, and saved the other 2. (678.7 IP with a 1.83 ERA, 441 K, 98 BB, 18 HR) I know baseball stats from that era can look insane, but this is on another level.