Tools

Shift+S - Pointer Tool
Shift+G - Magnify Tool
Shift+C - Camera Tool
Shift+E - Entity Tool
Shift+B - Block Tool
Shift+A - Texture App Tool
Shift+T - Apply Current Texture
Shift+D - Decal Tool
Shift+X - Clipping Tool
Shift+V - Vertex Manipulation Tool
Shift+P - Path Tool

Clipboard/Selection

Ctrl+C - copy objects to clipboard (also ctrl+insert)
Ctrl+V - paste objects from clipboard (also shift+insert)
Ctrl+X - cut objects to clipboard (also shift+del)
Ctrl+E - center on selection (vertex/object) in all views
Shift+Q - clear selections
PgUp - previous selection in "hit" list
PgDn - next selection in "hit" list
Grid
[ - grid lower
] - grid higher
Shift+R - toggle grid on/off
Shift+W - toggle snap to grid
p - (with mouse cursor in 3D view) toggle 3D grid on and off

Grouping

Ctrl+G - group objects
Ctrl+U - ungroup objects
Carving/Hollowing
Ctrl+Shift+C - carve
Ctrl+H - hollow
Creating Objects
Enter - create object drawn with block/entity tool
Alt+Shift+C - insert original prefab
Ctrl+R - create prefab with selected objects
Ctrl+T - create entity with selected objects; to add objects to an existing entity, select it and the objects and hit Ctrl+T (you will be prompted)
Other Object Operations
Ctrl+B - snap selected objects to grid (based on bounding box)
Alt+Enter - selected object's properties

File Stuff

Ctrl+N - new file
Ctrl+O - open file
Ctrl+S - save file
Undo/Redo
Ctrl+Z - undo
Ctrl+Y - redo
2D Views
Ctrl+I - flip vertical
Ctrl+L - flip horizontal
Tab - switch view types (top/side/front)
+/- - zoom in/out (hold Ctrl to synchronize all 2D views)
1 to 9 - preset zoom levels
Space - hold space and left mouse button to drag view
Alt - disable snap to grid while dragging with the mouse
3D View

Space - While holding the spacebar:

holding the left mouse button allows you to rotate your angle of view in any direction, while the viewing point remains stationary.

holding the right mouse button will allow you to move left, right, up, and down while keeping the viewing angle constant.

Space+Shift - While holding the spacebar and Shift:

the left mouse button acts the same as above.

the right mouse button allows you to move forward and backward, as well as from side to side.

z - Pressing the (lowercase) z puts the Worldcraft 3D view into its new "noclip" mode (this mode can be disabled in the 3D options dialog)

the mouse acts like +mlook is on (moving it around will change the player's direction of focus).

W - forward

S - backward

A - strafe left

D - strafe right

Shift+Right-mouse-click - will select an entire brush and bring up the 3D View context menu, as above.

p - (with mouse cursor in 3D view) toggle 3D grid on and off

o - (with mouse cursor in 3D view) display frames per second and yaw/pitch of camera.

Morph Tool

Ctrl+F - split faces (vertex manipulation) - must have two edges or vertices selected

Alt+E - vertex scaling

Selection Tool

Ctrl - hold Ctrl and click to select multiple objects

Shift - hold Shift when rotating to constrain rotation to 15 degrees; hold Shift when moving an object to create a copy (clone) of that object

(drag) - hold left mouse button and drag to select with a box; press Enter to select objects hitting the box, or press Shift+Enter to select objects only entirely within the box.

Camera Tool

Shift - create a new camera by holding Shift and dragging with the left mouse button.

PgUp - cycle to the previous camera position

PgDn - cycle to the next camera position

Delete - delete the current camera position

Clipper Tool

Enter - perform clip

Ctrl - hold Ctrl and drag with the left mouse button to move both handles of the clipper

Shift - hold Shift and drag with the left mouse button to create a new clip plane without performing the previous clip.

o - (with mouse cursor in 2D view) toggle clip sizes on and off

Miscellaneous

Alt+B - export again
Ctrl+A - auto-size 4 views to center
Shift - (while in Texture Application mode) select entire object
Shift+L - texture lock
Shift+Z - maximize/restore view
Ctrl+M - transform dialog
Alt+P - check map for errors
F9 - run map
Escape - abort current tool/mouse operation (drag/drop)
(content from wc guide list of hotkeys)