Editor Hotkeys
Spinners
You can Left-Click and drag the mouse up and down on spinner arrows to move the value up or down more rapidly.
Hold Alt to halve the value it moves by, or Shift to double it.
Right-Click on the spinner arrows to reset the value to its default value (typically 0, but 1 texture scale).
Panels
O Toggle the Outliner Panel (The Scene Tree)
I Toggle the Inspector Panel (Object Properties)
B Toggle the Browser Panel (Assets)
Global Tools
Q Select tool
W Translate tool
E Rotate tool
R Scale tool
T Texture tool
Viewports
F Focus camera on selected object
Enter Toggle maximized viewport
Numpad 1 Front viewport
Numpad 3 Right viewport
Numpad 7 Top viewport
Numpad 9 Perspective viewport
F2 Toggle wireframe in any viewport
F3 Toggle textures in 3D viewport
F4 Toggle lightmaps in 3D viewport
Grid
G Toggle grid
[ and ] Decrease and increase grid by power of two
Control + [ and ] Decrease and increase rotation snap by 5 degrees
Alt + [ and ] Decrease and increase grid opacity
Hold X Temporarily Disable/Enable grid/rotation snapping while manipulating object
Hold V Temporarily Disable/Enable vertex snapping while manipulating object
Building
Control + B Build new map changes
Control + Alt + B Force rebuild map from scratch (includes lighting)
L Build only unlit surfaces
Control + Alt + L Force rebuild lighting from scratch
F5 Build map and play from start position
Shift + F5 Build map and play from camera position