There really is nothing like comics to tax the limits of drawing and imagination.

On the tools aspect, I'm a fan of Microns and the Pentel Pocket Brush Pen, although I do tend to work digitally a lot more nowadays. I've been thinking about gravitating back to bristol board and ink though... there's nothing quite like a physically finished page. I imagine I'd still do layouts and rough drawing digitally, that's where the ability to undo, play around, and transform are immensely useful.