I added up a score for myself from that list giving me one point for something that more-or-less matches an item from this list and a half point for something vaguely similar. I got 15.5

The compiler, chess engine, and text-editor have been targets for years but I haven't quite gotten around to doing them.

I like the idea of the bitwise challenge.

I had been thinking that another challenge that I'd like to see (and have a go at) might be a plotPixel Challenge.

Make a game that does all rendering with

    PlotPixel(x : int, y : int, color:??? )
    NextFrame(offScreen:boolean = true, clearNow:boolean =true, clearColor:??? =0)

Unsure on byte for 256 indexed color or 32 bit for setting 24 bit color from ARGB as r= rA+R, g=gA+G, b=b*A+B.

It would be easy enough to test if a game obeyed the rules because a full video capture of the game should be possible by intercepting just those functions.

Perhaps a (generous) source code size constraint to stop people going too crazy. (maybe 64/128/256k source-code, zipped). Not for code golfing as much as to avoid people trying to squeeze Crysis though a straw.