* X during startup - Force Mac OS X startup
* option - (eventually) brings up a screen with startup volume choices
* Option-Command-Shift-Delete - Bypass primary startup volume and seek
a different startup volume (such as a CD or external disk)
* C - Start up from a CD that has a system folder
* N - Attempt to start up from a compatible network server (NetBoot)
* T - Start up in FireWire Target Disk mode (very handy for plugging your
Mac into another as an external hard drive)
* Shift - start up in Safe Boot mode and temporarily disable login items and
non-essential kernel extension files (Mac OS X 10.2 and later)
* Command-V - Start up in Verbose mode.
* Command-S - Start up in Single-User mode
* cmd-opt-p-r - Zap PRAM. Hold down until second chime.
* cmd-opt-n-v - Clear NV RAM. Similar to reset-all in Open Firmware.
* cmd-opt-o-f - Boot into open firmware
* hold mouse click - force eject a CD/DVD

http://davespicks.com/writing/programming/mackeys.html
On Boot
Key Combination Effect
mouse down Eject removable media ( I think Boot ROMs prior to 2.4f1 excluded the CD drive )
opt Bring up OF system picker on New World machines - boot to 9 on pre-New World machines
F8 Bring up Mac OS X boot partition selector (DTKs only?)
cmd-period When OF system picker is active, open the CD tray
cmd-opt Hold down until 2nd chime, will boot into Mac OS 9 ?
cmd-x (or just x?) Will boot into Mac OS X if 9 and X are on the same partition and that?fs the partition you?fre booting from.
cmd-opt-n-d prevent native drivers from loading (System 7 until 9.x?)
cmd-opt-shift-delete Bypass startup drive and boot from external (or CD). This actually forces the system to NOT load the driver for the default volume, which has the side effect mentioned above. For SCSI devices it searches from highest ID to lowest for a partition with a bootable system. Not sure about IDE drives.
cmd-opt-shift-delete-# Boot from a specific SCSI ID # (# = SCSI ID number)
cmd-opt-p-r Zap PRAM. Hold down until second chime.
cmd-opt-n-v Clear NV RAM. Similar to reset-all in Open Firmware.
cmd-opt-o-f Boot into open firmware
cmd-opt-t-v Force Quadra AV machines to use TV as a monitor
cmd-opt-x-o Boot from ROM (Mac Classic only)
cmd-opt-a-v Force an AV monitor to be recognized as one
c Boot from CD. If set to boot to X and no CD is present, may boot to 9.
d Force the internal hard disk to be the startup device
n Hold down until Mac logo, will attempt to boot from network server (using BOOTP or TFTP)
r Force PowerBooks to reset the screen
t Put FireWire machine into FireWire Target Disk mode
z Attempt to boot using the devalias zip from first bootable partition found
ctl-cmd-shift-power Reset power manager (with computer off)
shift (Classic only) Disable Extensions
shift (OS X, 10.1.3 and later) Disables login items. Also disables non-essential kernel extensions (safe boot mode)
cmd (Classic only) Boot with Virtual Memory off
cmd-v (OS X only) show console messages (verbose mose) during boot. Also invokes Safe Mode
cmd-s (OS X only) boot into single user mode
cmd-opt-c-i (Mac IIci only) Set date to 20 Sep 1989 to get a graphical easter egg
cmd-opt-f-x (Mac IIfx only) Set date to 19 Mar 1990 to get a graphical easter egg
cmd-opt-shift-tab-delete Erase startup disk under 7.1(?)


After display of Happy Mac icon
Key Combination Effect
space (Classic only) Invoke Extensions Manager
shift (Classic only) Disable Extensions including MacsBug
shift-opt (Classic only) Disable exetensions, except MacsBug
ctrl (Classic only) Break into MacsBug as soon as it is loaded


At login window
Key Combination Effect
shift (10.x only) Disable auto-login, forcing login window

As Finder Starts
Key Combination Effect
cmd-opt (whenever Classic Finder sees a new disk) Rebuild Desktop
opt (Mac OS 9) Do not open Finder windows
shift (Mac OS X) Do not launch startup items. Do not open Finder windows when launching Finder. The windows?f states aren?ft changed to closed, as they will be reopened if you reboot again.
shift (Mac OS 9) Do not launch anything from the "Startup Items" folder.


In Finder
opt-click close box (or cmd-opt-w) Close all open finder windows (except popup windows)
cmd-shift-opt-w Close all open finder windows (including popup windows)
cmd-right arrow Open folder in list view
cmd-opt-right arrow Recursively open folder and nested folders in list view
cmd-left arrow Close folder in list view
cmd-opt-left arrow Recursively close folder and nested folders in list view
cmd-up arrow Open parent folder. On Mac OS X, when nothing is selected and no windows are open, open User directory
cmd-opt-up arrow Open parent folder, closing current folder
cmd-opt-shift-up arrow Make desktop the active window, select parent volume
cmd-down arrow Open selected item. On Mac OS X, when nothing is selected and no windows are open, open the desktop folder
cmd-opt-down arrow Open selected item, closing current folder
cmd-opt-o Open selected item, closing current folder
opt-double-click Open selected item, closing current folder
opt-click (In disclosure triangle) expand or collapse all folders within that window
tab select next icon alphabetically
shift-tab select previous item alphabetically
cmd-delete move selection to trash
cmd-shift-delete empty trash
space while navigating, opens folder under mouse immediately (with spring-loaded folders enabled)

In Finder Window Menu
cmd-select Close window
cmd-shift-select Put away popup window
cmd-opt-select Expand selected window and close all others
ctl-select Expand selected window and collapse all others
ctl-opt-select Activate selected window and expand all others


On disk mount
cmd-opt (whenever Classic Finder sees a new disk) Rebuild Desktop
opt (Mac OS 9) Add session numbers (;1, ;2, etc) to ISO-9660 CD filenames
opt (Mac OS X) Show each session on an ISO-9660 CD as a volume
cmd-opt-i Force-mount ISO-9660 partition of a CD, rather than a Mac partition


After startup
Key Combination Effect

On machines with a power key
power Bring up dialog for shutdown, sleep or restart (see next table)
cmd-ctrl-power Unconditionally reboot (sometimes referred to as ?gcontrol flower power?h to easily remember) (dirty reboot - may corrupt disk)
ctrl-cmd-opt-power Fast shutdown
cmd-power Bring up debugger (if debugger installed). Really old macs (mac ii era) needed Paul Mercer?fs debugger init to do this, then it got folded into the firmware, around 040 timeframe.
cmd-opt-power Put late model PowerBooks & Desktops to sleep
cmd-opt-ctrl-power (PowerBook 500) Reset Power Manager
shift-fn-ctrl-power (PowerBook G3, G4) Reset Power Manager

On machines without a power key
ctrl-eject Bring up dialog for shutdown, sleep or restart (see next table)
cmd-ctrl-eject Unconditionally reboot
ctrl-cmd-opt-eject Fast shutdown
cmd-eject Bring up debugger (if debugger installed). Really old macs (mac ii era) needed Paul Mercer?fs debugger init to do this, then it got folded into the firmware, around 040 timeframe.
cmd-opt-eject Put late model PowerBooks & Desktops to sleep

On all machines
cmd-opt-esc Force quit current app
cmd-shift-0 Put late model PowerBooks & Desktops to sleep No longer work in OS X. On Macs with three floppy drives (Mac SE) they eject the third floppy disk.
cmd-shift-1 or 2 Eject internal or external floppy. Not sure which is which on dual floppy machines (Mac SE, Mac II, etc.)
cmd-shift-3 Screen shot
cmd-shift-4 Abstract user defined area screen shot (hold control while selecting to direct it to the clipboard on Mac OS 9)
cmd-shift-capslock-4 (Classic only) User selectable window screen shot
cmd-ctl-shift-3 Screen shot to clipboard
cmd-ctl-shift-4 Abstract user defined area screen shot to clipboard
cmd-ctl-shift-capslock-4 (Classic only) User selectable window screen shot to clipboard (classic only)
cmd-tab Switch apps (possible to change key in Mac OS 8-9)
cmd-shift-tab Switch apps in reverse order
cmd-space Switch keyboards/script systems (if more than one is installed)
cmd-opt-space switch through all keyboards in keyboards menu
opt-f3, opt-f4 or opt-f5 bring up the system preferences (Mac OS X only - maybe powerbooks only? only if system preferences isn?ft already running)
cmd-f1 toggle between video mirroring and extended desktop mode (works on Ti Powerbooks)
opt-f1 open the displays preference (10.2 and later)
cmd-f2 auto-detect a newly-connected display (works on Ti Powerbooks)
opt-f2 open the displays preference (10.2 and later)
opt-f3, f4, or f5 open the Sounds preference (10.2 and later)
opt-f8, f9, or f10 open the Keyboard and Mouse preference (10.2 and later)
f12 Eject CD/DVD (must be held down on 10.1.2 or later). If the device can be dismounted, it is. If not, nothing happens.
f14 dim display (cubes/g4 iMacs/others?)
f15 brighten display (cubes/g4 iMacs/others?)
cmd-ctl-shift-0 Spin down HD (when possible) on machines running OS 9
cmd-` cycle through current application?fs windows (Mac OS X 10.2 only?)
cmd-~ cycle through current application?fs windows (reverse order) (Mac OS X 10.2 only?)
opt-"Empty Trash" Emptry trash without locked file or contents summary alert. Empties locked items, as well
cmd-opt-D (Mac OS X only) toggle dock
cmd-opt (when opening chooser) (Mac OS 9 only) rebuild chooser cache of printer driver information

(See Universal Access System Preference for more on following)
cmd-opt-ctl-8 (Mac OS X, 10.2 or later) Turn on "Inverse Mode" via accessbility.
cmd-opt-8 (Mac OS X, 10.2 or later) Turn on "Zoom Mode" via accessbility.
cmd-opt-plus (Mac OS X, 10.2 or later) Zoom In via accessbility.
cmd-opt-minus (Mac OS X, 10.2 or later) Zoom Out via accessbility.


In the sleep/restart dialog
Key Effect
S Sleep
R Restart
esc cancel
cmd-. (period) cancel
Return or Enter Shut Down
Power Cancel (9.2.x only?)


In other dialogs
Key Action
esc Cancel
command-. (period) Cancel
enter Default button
return Default button (if there are no text fields that use return
cmd-d Don?ft save (in save/cancel/don?ft save dialog)
cmd-r Replace (in "Do you want to replace this file" dialog, Mac OS X only)


On keyboards with a function key
Key Combination Effect
fn-backspace forward delete
fn-left arrow home
fn-right arrow end
fn-up arrow page up
fn-down arrow page down


Clicks
click / modifier Effect
option-click in another application Switch to that application and hide previous app
cmd-drag (window) Drag window without bringing it to front (requires application support to work behind dialogs)
cmd-drag (window background) Pan contents of window with hand (Finder)
cmd-opt-drag (window background) Option may be needed to pan contents of window with hand (Finder) on 10.3 and later
cmd-drag (Mac OS X) Rearrange menu extras
opt-drag (file) Copy file
cmd-opt-drag (file) Make alias of file
cmd-click window title Pop-up menu showing path to current folder/document (in some applications)
option-windowshade Windowshade all windows of application (classic only)
option-zoom Zoom window to full-screen
option-yellow Dock all windows of application (Mac OS X only)
option-green Zoom window to fill screen (in some applications)

Mac OS X only - items in dock
cmd-click Reveal in Finder
cmd-opt-click Activate app and hide other apps
ctl-click (or click and hold) contextual menu
cmd-drag into dock Freeze current dock items from moving so icon can be dropped onto an app
cmd-opt-drag into dock Force application you?fre dropping onto to open dropped item


Control Strip
opt-drag control strip Move control strip
opt-drag CS module within strip reorders CS modules
opt-drag CS module to trash uninstalls a module
opt-drag CS module elsewhere whatever dragging the module file itself would