Share your button assignments / controller mappings

[FlightRisk]

It might be nice to compile a list of what keyboard keys, arcade buttons or controller mappings people find helpful.  What do you use for controlling LB/BB and what do you assign when playing a game? Whether you use RetroArch, MAME or other emulators, do you try to keep them all the same or have different mappings to be more true to the original setup for consoles? Share your tips and configurations that work for you.