What about Wheeljack? He'd probably be a very intense kind of kisser, until something distracted him and the next second he's all 'oh, what's this?' and then he runs off to his lab. Actually, I think all mechs with face guards are phenomenal kissers, but that's just me.

I also like to think that some of the least expected mechs are great kissers, too. Like Ultra Magnus or Pipes or something.