For me, I used to be like Violet, but a little while ago, I began experimenting and now I use an Xbox 360 controller with the following mappings:
Movement: Analogue Stick;
Jump: A;
Fire: RB or B;
Run: X;
Select: LB or Y.
This allows me to switch weapons(Left index finger), run(Right thumb), shoot(Right index), jump(Right thumb), and move(Left thumb) all at the same time without moving my fingers from their usual position.

If I'm on the keyboard, I either use default controls, or I choose whatever keyboard mappings I feel like using at the time(If I do this, I usually end up using the arrows, Shift, Z, X, and C). Although, if I have the option, I choose a controller.