How do I reconfigure keyboard shortcuts for copy and paste?

Solution 1:

Various config things needed changing to get the results I wanted:

• In Firefox, about:config
  ui.key.accelKey 18
  ui.key.menuAccessKey 17
  
  This makes the Alt+C, Alt+V and Alt+W the keyboard shortcuts for Firefox rather than the corresponding Ctrl keys.
• In gnome-terminal, edit->keyboard shortcuts, turn off "Enable menu access keys", change the copy, paste, etc., to Alt+C, Alt+V, etc. (This may have been the default that I changed some time in the past.)
• In .synergy-conf, remove alt = super, super = alt. Now, Alt on the Ubuntu keyboard is the Command key on the Mac. Now, I just use Alt instead of Win; no big deal. (The Unity window manager seems to "own" the Win key; it seemed the path of least resistance to just change my habit here... and the Alt key is more like the location of the Command key on the Mac.)
• Disable "New Terminal - Alt-T" in system keyboard shortcuts so it can be used for "New Tab" in gnome-terminal and Firefox.

Thanks for the pointers... I'd forgotten about the Firefox about:config change I had made way back when, which was an essential piece to the puzzle.

Solution 2:

Ctrl+C and Ctrl+V by default do not copy and paste in the Terminal. This is because Ctrl+C is a special command used (for decades) to interrupt a currently running process. The default instead is Shift+Ctrl+C and Shift+Ctrl+V.

If you want to, you change this by clicking Edit>Keyboard Shortcuts in your Terminal.