Lol definitely not the Epic 4G. I haven't seen a Sprint phone with a dev community since the OG Evo. Heck even though a lot of the devs left, it still has a better community than most phones. Anything you wanted, there was either a theme, mod, rom, kernel, etc.
But I'd say the OG Evo, Epic Touch, Galaxy Nexus, and I wouldn't be surprised if the Evo LTE had one...even though HTC encrypts the boot loaders. :/. The popularity of the phone is a huge factor.