Terrain

Render blocks in the right order so they show up correctly (see water).
Implement sinking in blocks, based on their density
Add option to change world (for example from save) during program execution without closing Window
make water spread to surrounding empty areas

Items

return extra amount to inventory if quick access is full?

Inventory

show player model in the inventory
add gear slots/handling
improve furnace GUI

Graphics

improve lighting system, add shadows (shadow mapping?)
shaders (motion blur?)
add shadows
add lamps light
add main menu with large project name/logo, save files manager, new world creation options and settings

Sounds

add new sounds
use ManagedSoundPlayer class (http://www.pyglet.org/doc/api/pyglet.media.ManagedSoundPlayer-class.html) or something better
add volume change option

Health

Improve damage from falling from too high.

Grass Expansion

improve performance
grass expansion in new thread

Misc

need place for brainstorming/ideas etc. related to project, so we can cooperate (IRC/forums/Reddit/mailing list?)
write more unit tests (tests.py)