Collectors have been quick to find variation cards in 2012 Topps Series 1. Browsing through eBay I see the following in addition to the short prints already announced by Topps (Reyes, Pujols, Squirrel):
#35 Eric Hosmer -- The variation shows Hosmer with several Royals teammates in the dugout.
#185 Pablo Sandoval -- The Panda punching the Pirates mascot.
#421 Heath Bell -- Don't see any other Heath Bell cards listed yet so can't confirm this one, but he is holding a jar of gumballs and since the card number is #421 then obviously it's some type of short print and there is no Heath Bell card in the preliminary base set checklist.
For pics and to follow the listings of these variation cards:
Complete 2012 Topps Short Print Checklist
2012 Topps #35 Eric Hosmer Variation
2012 Topps #185 Pablo Sandoval Variation
2012 Topps #421 Heath Bell Variation