Considering they need to be older, yet still in production phones, I would just about put money on the Evo 3D and/or the Conquest.
Nexus, no chance, too new, too exclusive and too expensive. The massive screen is too big of a jump and could steal people from postpaid. Same with the Galaxy S2. The Photon is also too new. The Evo Design and Epic are older and both have been rumored for Boost. The 3D has been rumored for Virgin, which fits with it being removed from Sprint's site, but not end of life'd.
Your village called, they want their idiot back.