A lot of us here at Massively have been spending a good amount of time with Mythos, so the subject of new classes definitely tickles our curiosity feelers. As of right now, there are three primary classes that each have three different styles of play. So really, it could be said that Mythos has nine classes total -- in a way. Our imaginations certainly become wild when we consider what kinds of experimental-fun a game like this could employ when adding more classes.
In-so-far as weapons go, there is definitely the possibility of a polearm class being created. Although we also have to wonder if the developers might be tempted to add in some eastern flavor ala a ninja-style class -- or assassin if you prefer.
A pet class with three wildly different styles of pet-play (currently two classes have a pet-style skill tree) could be a lot of fun although that really doesn't pertain to any kind of weapon. We just like the idea of a pet-focused class.
Or maybe a class that uses lightning magic, which admittedly isn't too experimental -- we just love zapping stuff with bolts of lightning no less than 1.21 jigowatts. One option would be to combine the assassin-style class with the lightning magic class. Yeah, we could probably go on all day, but that's definitely a class this particular blogger would play for many, many hours.