Wizard. I'm a physicist, so speaking in arcane languages comes naturally to me.
Apart from that, druid. I played one in our last campaign, and it became quite easy slipping into that role. The other PCs were constantly amazed about how little he cared about material wealth...
If I tally up all the classes I played. Its kinda odd, I've actually played the Cleric class the most. However, I've been at my best playing the Monk actually. So I put Monk down on the poll.