This is an mmorpg that is client-based, but it is a VERY lightweight file (around 15-25mb). This may make you think that it is bad, but it is worth looking at still. Movement is best with the arrow keys, you attack with control, and the mouse is mostly for doing things like picking up items or going through menus, but you can use it to walk too.
Kind of reminds me of Maplestory.
It's isometric, by the way, but it isn't grainy. (:D)
http://www.endless-online.com/