I've taken to playing doom with a gamepad recently. Zdoom has wonderful gamepad support.
Only, it's difficult to play hexen/heretic with a gamepad because there is a lack of buttons on a logitech dual action gamepad.
Hexen for the psx got around this by having one button used as a type of "shift" button. I believe it was one of the shoulder buttons. Anyways, this allowed all of the needed functions to be used with the limited amount of buttons on the gamepad.
A button pressed by it's self would perform one specific function like switching weapons. The same button could then be pressed at the same time the "shift" button is being held down and perform a different function like changing items instead.
Button without shift, fires weapon. Same button with shift, uses item.
Button without shift, jump. Button with shift, crouches.
Those are just more examples to get the point across.
It would be really great if there was a "shift" button that could be mapped to the gamepad as well as a way of mapping "shift + this button = this action" type of thing.
I hope I explained that clearly.
I couldn't find this brought up before, so forgive me if it has and I just missed it.