Platinum Arts Sandbox Cheatsheet!  Here is a list of the most basic commands.  
You might want to print this document! For more check out the in game help menu.

Press the spacebar to jump
Use the arrow keys to move or w,a,s,d
Hit ESC to enter the menu
Press E to edit and E again to go back into world Mode
Click on what you want to edit - You can drag the mouse to select more area
Use the mousewheel to push and pull your selection
Hit the Jump key to deselect (default Spacebar)
Third Mouse Buttom/Pushing Mouse WHeel - Area select
F1 - New Map Model (Or edit mode in the RPG)
F2 or Y + Mouse Wheel to change textures - Shift 0 covers all sides
F3 Material and quick edit menu
F4 Skybox  Editor
F5 Entity Search
F6 Script/Config Editor
F7 Entity Helper Options
Q + Mouse Wheel to push and pull a corner
F + Mouse Wheel to push and pull all 4 corners at once
R + Mouse Wheel to rotate
G + Mouse Wheel to change the grid size
H enters heightmap mode.  Select a created block and scroll the mouse wheel
Z to undo one step
C copy
V paste
L turns on fullbright, easy way to see models properly (must be in edit mode)
X to mirror relative to the side of the white box
F12 - Takes a screenshot
Backspace deletes an entity
. edits an entity (select the entity and press to change values)

` (above tab) or T to enter the command prompt
Command Prompt Entries
/savemap mapname to save your map (change mapname to what you want to save as)
/map mapname (loads the map mapname) (type map and hit tab to scroll available maps)
editmat water  (creates water when you forward scroll)