The most talked about and most recognized class the Mesmer was revealed by ArenaNet. They kept their promise on topping off the professions before the year was up. Although I am not super familiar with how the classed worked in the original Guild Wars, I am still satisfied by what has become of it. I knew the Mesmer has the unique ability of doing damage to players by throwing debuffs on them that make it so that they hurt themselves when they executed abilities.
That has carried to the Mesmer in Guild Wars 2. They have access to a unique condition that they can place on enemies called Confusion. When placed on an enemy they take damage every time they use one of their abilities. The confusion condition stacks and can do immense damage to enemies who are skill happy.
The Mesmers are a three-part story, they have Illusions, Mantras, and Shatter effects. Illusions allow Mesmers to create a mind trick in the game. They come in two parts, Clones and Phantasms. The clones are the weaker of the two and mimic the Mesmer. They have low health and do little damage, so I am assuming these are best used when you want to distract your opponent for a moment while you set yourself up with something else.