I made a row of 12 Atari-Volcano style buttons across the top edge of my panel, right where the panel meets the bezel, for admin functions.
3 groups of 4 buttons:
1) Esc, Enter, Tab and ~.
2) Pause, F2 (operator settings for many games), 9 (service coin) and a blank in case I missed something (still blank after 4 years).
3) Another blank, F1 (crosshair toggle for gun games), F3 (game reset), and F10 (I forget what it is in MAME, but I know it comes in handy on Stella, the Atari 2600 emu; it's also important in Ur-Quan Masters[Star Control 2]).
I use all of those fairly regularly (you'll REALLY wish you put Pause on there if you don't). I do have to go to the keyboard now and then, but mainly for save states.