My 4 player cab has the following:
Tab
Tilda(~)
Enter
Esc
Reset
Pause (left side)
Pause (right side)
Left Pinball button
Right Pinball button
Plunger button (just for fun)
Player1 Start
Player2 Start
Player3 Start
Player4 Start
Player1 CoinUp
Player2 CoinUp
Player3 CoinUp
Player4 CoinUp
7 buttons next to player1 8-way joystick
4 buttons next to player1 4-way joystick
7 buttons next to player2 8-way joystick
6 buttons next to player3 8-way joystick
6 buttons next to player4 8-way joystick
Left Mouse click button
Right Mouse click button
Also.....since I am using a keyboard encoder (which allows multiple characters to be mapped a single button press), I decided to add a few buttons extra. The idea being that when I press one of these buttons, I could execute a BAT file which would then run a command to reconfigure by keyboard encoder button mappings. As a result, if I wanted to play TombRaider, I could hit the TombRaider button and have all the switches on my Mame Cabinet remapped correctly for me to play TombRaider. Another button press would take me back to the Mame Configuration mappings.......
PS: I have two pause buttons located on separate sides of the control panel top so any player (1-4) would be able to reach the Pause button quickly (ie: in case they have to leave quickly to take a leak during a heavy night of beer drinking and Mame competition).....

I knew I was only going to build one 4-player cabinet, so I wanted it to be excellent since it will be in my family for a very long time.....
Later
UncleT