For me, it's the ctrl+d (duplicate) shortcut that I discovered 5 minutes ago, which combines ctrl+c and ctrl+v.
autogen has collected all the advice in one post. It can be found in the middle of page 17. Here's the post for your convenience. I'll try to see if I can be bothered updating this post. Until then, send a thank-you-pm to autogen
As far as I know, PC users substitute 'COMMAND' with 'ALT' and 'ALT' with 'CTRL'
Live shortcuts & alternative controls for certain functions.
Duplicate = COMMAND+D.
Disable Grid = COMMAND+4 (or hold COMMAND whilst selecting note or note start/end).
Select Looped = COMMAND+SHIFT+L.
Resize/Move Loop braces = cursor keys or COMMAND+cursor keys.
In arrange view loop selected = COMMAND+L.
In arrange view consolidate multiple selected clips = COMMAND+J.
Playback from current position = SHIFT+SPACEBAR.
Trigger selected clip slot = RETURN.
Switch Clip/Track view = SHIFT+TAB.
Move clip from session to arrange & vica versa = Click and hold on clip then press TAB.
Stop focus moving when triggering clips (all clips) = In prefs > Record/Warp/Launch > Select on Launch > select 'off'.
Stop focus moving when triggering clips (selected clips) = CTRL+Click desired clip > select 'Select on Launch (Pref)'.
Preferences = COMMAND+,.
Adjust all track widths = hold ALT while adjusting.
Record Enable Track = F9.
Slower response while changing track levels = Hold COMMAND while moving fader.
Show hide plugin windows = COMMAND+ALT+P.
Stop browser preview = ESC.
In browser alternate navigation/previewing = left & right cursor keys.
Zoom to loop = Click on the word "length".
Zoom to position = Click on the word "position".
Zoom out 100% = Double click the bottom clip overview tab.
Zoom to specific portion = Use start and end of bottom clip overview like loop braces.
Alternate scrolling in MIDI clips = COMMAND+ALT+Drag.
Show/Hide overview in session view = COMMAND+ALT+O.
Show/Hide Info View = SHIFT+/.
Mute/Unmute tracks 1-8 = F1-F8.
Time compress/expand MIDI notes = right-click with all notes selected then select 'stretch notes'.
Insert silence in arrange view/scene in session view = COMMAND+I.
Drag multiple files to individual tracks = Hold COMMAND whilst dragging files in.
Unfold all arrange tracks = ALT+Click a track arrow icon.
Alternative velocity control in MIDI editor = COMMAND+Click note+drag.
Duplicate note in MIDI editor = ALT+Click note+drag.
Render tracks as individual files = In render dialog change "Master" to "All Tracks".
Assign twice as many qwerty keys to live = SHIFT.
Restrict automation point movement to vertical axis = COMMAND+Drag.
Scroll drum racks 1 row at a time = COMMAND+Drag.
View multiple plugin windows = In prefs > Look/Feel > Auto-Hide Plugin Windows > select 'off'.
Edit info text for tracks and devices to make notes = CTRL+Click > select 'Edit Info Text'.
Create note with draw mode off = Double Click.
Remove stop buttons to avoid clips stopping when changing scenes = Select clip slot > COMMAND+E (or enable 'Legato' launch mode).
*Hidden buttons visible when in midi or key assign mode =
scene up/down (in master track).
per track play button - launches selected clip in track.
*Entering bpm in the scene launch buttons title sets bpm when launched.
*Click the headphone icon in midi editor to enable vertical keyboard to preview related sound.
*While MIDI synced to external machine hosting Live ALT+SPACEBAR on the sync slave causes it to sync to the masters current song position. (remedy for sync drifting without stopping and starting).
*Remember to experiment with the default live rack presets especially the DJ/Performance ones.
*GIGA libraries can be exported to Sampler then deleted (if required), as all samples are copied to the library.
*Mac users check out a free app called Soundsource. It adds an audio prefs selector to the menu-bar.
*OSX Function keys = ALT+F1/F2 opens Display Prefs, ALT+F3/F4/F5 opens Sound Prefs, ALT+F8/F9/F10 opens Keyboard & Mouse Prefs.
*When a new version of Live is released. Open Info Window (SHIFT+/) and hover any new parameters, fields or preferences.
*Multiple tracks can be selected and frozen simultaneously.
*Drag and drop tracks directly from iTunes for DJing.
*Dragging a sample onto a plugin instrument will replace the instrument with an instance of Simpler containing that sample.