1   Emacs

Emacs have a LOT of nice key bindings that you may want to know. I'll list the ones that are very useful and possibly hard to find.

C (Control), X (Meta), E (Escape), S (Shift).

C-k	Cut to end of line to killring.
C-y	Paste entry in killring.
E-y	Go back in killring and paste that instead.
C-x C-f	Find file.
C-x C-s	Save.
C-x k	Kill buffer (not delete file)
C-s C-w	Save as.
C-s	Search.
M-% | M-S-2 (sv)	Search and replace.
C-g	Abort, quit.
C-_ | C-S-- (sv)	Undo.
C-a	Go to beginning of line.
C-e	Go to end of line.
C-x C-q	Check out/in(C-c C-c to submit that) from/to RCS.
C-q whatever	Force writing of exactly that key without treating it as a command.
M-x commandstring	All emacs commands are available this way.
C-space	Mark selection start
ESC-w	Copy
C-w	Cut

2   General unix

C-a	Go to beginning of line.
C-e	Go to end of line.
TAB	Tab completion.

3   Screen

C-a C-g	Switch to audio bell.
C-a g	Switch to screen bell.