Its been mentioned many many times already...

But Musketeer (Musket..man/lady?) Would branch from Archer ofcourse, and be a pure ranged DPS class.
Its gameplay mechanic, I'm thinking sorta like SWTOR's Sniper, without the lovely shield ofcourse...
But using a rifle, and have to stay stationary for most of his abillities, while still being able to use a few abillities on the move.