In WR:SR (a Industrial City-Building Economy and Transport Simulator), there are different placing and overlay modes, like Snap-to-Grid (L4), Elevation (R4) and Underground view (R5), but I still need the first two buttons for zooming/radius(L1,R1), placing(R2)/removal(R2) confirm and the small buttons for placement elevation (for road/rails (and their bridges), pipes/cables) (X,B), mirroring (Y). (I forgot what A was for).

Basically every time you need more than two keys on the keyboard and the mouse simultanously, for the equivalent on the SD, the lower backbuttons come in handy.

I have a game that I was afraid of figuring out the controls yet; it is Cataclysm: Dark Days Ahead. In this game I will likely need every available button twice or something.