As for the answer? Oooooh, that’s a tough one. However, if I was forced to answer with only one tool, I’d have to go with the trusty Staedtler Karat Aqaurell (125-30) pencil, which I find feels really, really nice to draw with.
It’s also handy because it has a photo-proof blue colour, which is easily digitally removed after scanning my final inked pieces, which means I don’t have to deal with the mess of erasing my pencil lines by hand.
I’ve been using that particular pencil for years now, and I can see myself using it for many years hence.