Monty got an HTC Thunderbolt and wants to know what the most recent Android is to breathe new life into it. Leo says that the oldest phones are the best candidates for new firmware and mods.
Leo suggests going to XDA Developer Forums to learn how to root that phone and install the most recent Android OS for it. Then, go to Google Play and install ClockworkMod. Find the Cyanogen (CM10) mod. Leo advises getting the stable build. It'll make that Thunderbolt considerably faster.