Beatfader

This is the most fun I've had playing drums with a MIDI controller. Really simplifies playing live as an option. Works with knobs too, if your controller doesn't have any sliders. Sound selection is solid, and the ability to route your own drum rack through Beatfader means limitless sound design options. Maybe not what I'll always grab when creating a drum part, since playing pads provides more control especially for recording, but definitely stays on the short list.