I'd like to see someone make a knife without using any modern technology precursors whatsoever. That means starting from using ones hands and what is available from nature in its natural form. I think it'd be quite an accomplishment.
I've never done it. It's incredibly time consuming but satisfying, from the first hand accounts I've read. You can cut hours or days off of your work time by using modern tools for some of the most seemingly trivial steps.