Brush category section. (Allowing to place different brush types - Grunge, abstract, inking etc)
Snap to! (ESPECIALLY with things like the rotate tool. Example, holding shift while rotating will snap to 0,90,180, 270 degrees)
(Straight) line tool - Holding shift while drawing creates a straight line
Brush types from Deviant arts Muro
Brush types from Harmony (seems to be frequently requested)
bigger colour pallet save things (where you drag the colours to it)
Custom keybindings.
scatter parameter (perhaps it's already in there?)
Will add more, I had a ton but had a brain fart