Rewind button.

[sexist pigdog]

Breasts on female buttocks. Infact, go the whole hog and stick some behind the knees and on the back of their heels, too…

[/sexist pigdog]

A nice simple 34 fork with coil spring and simple rebound only damping.
Like my old 36 van r but a but lighter

9 speed clutch mech

A gizmo that would let you use shimano shifters with Sram Mechs, or vice versa. Some kind of in-line cable pull length amender.

And, like others have said, simple short travel forks that don’t cost the earth by doing away with multiple adjustment options, lock outs and other fangle dangle gizmos. I have a pair of Marzzochi forks from way back which are like this, and they still work fine.

-Midge bars with 22.2mm ends so I can use hydro mtb disc brake levers.
-50mm carbon rims
-CHeap version of a Shand Stoater Plus

orangeboy, wouldn’t the Marzocchi 55R fit your criteria, or too heavy?

http://www.ukbikestore.co.uk/product/353/9141100s/marzocchi-55-r-26-fork-2014-1-18-steerer.html

Edit: 2.5kg, maybe a bit heavy but not that bad. And £320 new…

1 1/8 steerer Pikes

Spokeless wheels
Wireless brakes and gears
Self-inflating tyres
Invisibility cloak (a security device that’s better than a lock)